diff --git a/src/epub_converter/html_epub_preprocessor.py b/src/epub_converter/html_epub_preprocessor.py
index 6561662..c40c1ff 100644
--- a/src/epub_converter/html_epub_preprocessor.py
+++ b/src/epub_converter/html_epub_preprocessor.py
@@ -10,7 +10,7 @@ from src.livecarta_config import LiveCartaConfig
 
 
 def save_image_locally(img_file_path, img_content, book_id):
-    """ Function saves all images locally """
+    """Function saves all images locally"""
     folder_path = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
     new_path = pathlib.Path(os.path.join(
         folder_path, f'../json/img_{book_id}/'))
@@ -25,7 +25,7 @@ def save_image_locally(img_file_path, img_content, book_id):
 
 
 def save_image_to_aws(access: Access, img_file_path, img_content: bytes, book_id):
-    """ Function saves all images to Amazon web service """
+    """Function saves all images to Amazon web service"""
     link_path = access.send_image(
         img_file_path, doc_id=book_id, img_content=img_content)
     return link_path
@@ -37,7 +37,7 @@ def update_images_src_links(body_tag: Tag,
                             access=None,
                             path2aws_path=None,
                             book_id=None):
-    """ Function makes dictionary image_src_path -> Amazon web service_path """
+    """Function makes dictionary image_src_path -> Amazon web service_path"""
     img_tags = body_tag.find_all('img')
 
     for img in img_tags:
@@ -72,7 +72,7 @@ def update_images_src_links(body_tag: Tag,
 
 
 def preprocess_table(body_tag: BeautifulSoup):
-    """ Function to preprocess tables and tags(td|th|tr): style """
+    """Function to preprocess tables and tags(td|th|tr): style"""
     tables = body_tag.find_all("table")
     for table in tables:
         ts = table.find_all(re.compile("td|th|tr"))
@@ -84,13 +84,13 @@ def preprocess_table(body_tag: BeautifulSoup):
                     r"[^-]width: ?(\d+\.?\d*)(p[tx])", style)
                 if width_match:
                     size = width_match.group(1)
-                    units = width_match.group(2)
                     width = size+'px'
 
             t_tag.attrs['width'] = t_tag.get('width') or width
 
             if t_tag.attrs.get('style'):
-                t_tag.attrs['style'] = t_tag.attrs['style'].replace('border:0;', '')
+                t_tag.attrs['style'] = t_tag.attrs['style'].replace(
+                    'border:0;', '')
 
             elif t_tag.attrs.get('style') == '':
                 del t_tag.attrs['style']
@@ -113,7 +113,7 @@ def process_lists(body_tag):
 
 
 def insert_span_with_attrs_before_tag(main_tag, tag, id_, class_):
-    """ Function inserts span before tag to be removed(aren't supported by livecarta) """
+    """Function inserts span before tag to be removed(aren't supported by livecarta)"""
     new_tag = main_tag.new_tag("span")
     new_tag.attrs['id'] = id_ or ''
     new_tag.attrs['class'] = class_ or ''
@@ -157,7 +157,7 @@ def clean_headings_content(content: Tag, title: str):
 
 
 def heading_tag_to_p_tag(body_tag):
-    """ Function to convert all lower level headings to p tags """
+    """Function to convert all lower level headings to p tags"""
     pattern = f'^h[{LiveCartaConfig.SUPPORTED_LEVELS + 1}-9]$'
     header_tags = body_tag.find_all(re.compile(pattern))
     for tag in header_tags:
@@ -165,7 +165,7 @@ def heading_tag_to_p_tag(body_tag):
 
 
 def clean_title_from_numbering(title: str):
-    """ Function removes numbering from titles """
+    """Function removes numbering from titles"""
     title = re.sub(r'^(\s+)+', '', title)
     # title = re.sub(r'^(?:\.?\d+\.? ?)+', '', title) # delete chapter numbering from the title
     # title = re.sub(r'^(?:\.?[MDCLXVIclxvi]+\.? ?)+ ', '', title)  # delete chapter numbering(letters) from the title
@@ -174,7 +174,7 @@ def clean_title_from_numbering(title: str):
 
 
 def replace_with_livecarta_anchor_tag(anchor, i):
-    """ Function replace noteref_tag(anchor) with new livecarta tag """
+    """Function replace noteref_tag(anchor) with new livecarta tag"""
     new_tag = BeautifulSoup(features='lxml').new_tag('sup')
     new_tag['class'] = 'footnote-element'
     new_tag['data-id'] = i + 1
@@ -194,7 +194,7 @@ def preprocess_footnotes(source_html_tag: Tag, href2soup_html: dict = None, note
 
     <p>Here is an example footnote<sup><a epub:type="noteref" href="#n1">1</a></sup></p>
     <aside epub:type="footnote" id="n1"><p>With a footnote here.</p></aside>
-    """
+   """
     footnotes = []
     noterefs_tags = source_html_tag.find_all(
         attrs={noteref_attr_name: 'noteref'})
@@ -207,13 +207,13 @@ def preprocess_footnotes(source_html_tag: Tag, href2soup_html: dict = None, note
     [tag.decompose() for tag in bad_noterefs_tags]
 
     def parse_a_tag_href(s: str) -> Tuple[str, str]:
-        """ Returns name of file & id of an anchor """
+        """Returns name of file & id of an anchor"""
         assert '#' in s, f'Error. Unexpected href: {s} in a tag. Href must contain an id.'
         f, id_ = s.split('#')
         return f, id_
 
     def verify_footnote_tag(tags: list):
-        """ Function verifies is tag - footnote """
+        """Function verifies is tag - footnote"""
         assert len(tags) <= 1, f'Error, Multiple id: {href}.\n{tags}'
         if len(tags) == 0:
             anchored_tags = list(target_html_tag.find_all(id=element_id))
@@ -259,9 +259,7 @@ def preprocess_footnotes(source_html_tag: Tag, href2soup_html: dict = None, note
 
 
 def unwrap_structural_tags(body_tag):
-    """
-    Main function that works with structure of html.
-    Make changes inplace.
+    """Main function that works with structure of html. Make changes inplace.
 
     1. Extracts tags that are not needed
 
@@ -278,7 +276,7 @@ def unwrap_structural_tags(body_tag):
     """
 
     def _preserve_class_in_aside_tag(tag_):
-        """ to save css style inherited from class, copy class to aside tag (which is parent to tag_) """
+        """to save css style inherited from class, copy class to aside tag (which is parent to tag_)"""
         # this is for Wiley books with boxes
         tag_class = tag_.attrs['class'] if not isinstance(
             tag_.attrs['class'], list) else tag_.attrs['class'][0]
@@ -434,14 +432,23 @@ def unwrap_structural_tags(body_tag):
 
 
 def get_tags_between_chapter_marks(first_id, href, html_soup):
-    """
-    After processing on a first_id that corresponds to current chapter,
+    """After processing on a first_id that corresponds to current chapter,
     from initial html_soup all tags from current chapter are extracted
 
-    :param first_id: id that point where a chapter starts. A Tag with class: 'converter-chapter-mark'
-    :param href: name of current chapter's file
-    :param html_soup: soup object of current  file
-    :return: list [Tag, NavigableString]; chapter's tags
+    Parameters
+    ----------
+    first_id :
+        Id that point where a chapter starts. A Tag with class: 'converter-chapter-mark'
+    href :
+        Name of current chapter's file
+    html_soup :
+        Soup object of current  file
+
+    Returns
+    -------
+    tags : list [Tag, NavigableString]
+        Chapter's tags
+
     """
     marked_tags = html_soup.find(
         attrs={'id': first_id, 'class': 'converter-chapter-mark'})
@@ -467,7 +474,7 @@ def get_tags_between_chapter_marks(first_id, href, html_soup):
 
 
 def wrap_block_tag_with_table(main_tag, old_tag, width='95', border='1px', bg_color=None):
-    """ Function wraps <block> with <table> """
+    """Function wraps <block> with <table>"""
     table = main_tag.new_tag("table")
     table.attrs['border'] = border
     table.attrs['align'] = 'center'
@@ -497,7 +504,7 @@ def clean_wiley_block(block):
 
 
 def preprocess_block_tags(chapter_tag):
-    """ Function preprocessing <block> tags """
+    """Function preprocessing <block> tags"""
     for block in chapter_tag.find_all("blockquote"):
         if block.attrs.get('class') in ['feature1', 'feature2', 'feature3', 'feature4']:
             clean_wiley_block(block)
@@ -520,7 +527,7 @@ def preprocess_block_tags(chapter_tag):
 
 
 def prepare_formatted(text):
-    """ Function replaces special symbols with their Unicode representation """
+    """Function replaces special symbols with their Unicode representation"""
     text = text.replace("<", "\x3C")
     text = text.replace(">", "\x3E")
     text = text.replace('\t', "\xa0 \xa0 ")  # &nbsp; &nbsp;
@@ -530,7 +537,7 @@ def prepare_formatted(text):
 
 
 def wrap_preformatted_span_with_table(main_tag, old_tag):
-    """ Function wraps <span> with <table> """
+    """Function wraps <span> with <table>"""
     table = main_tag.new_tag("table")
     table.attrs['border'] = '1px #ccc;'
     table.attrs['style'] = 'width:100%;'
@@ -547,7 +554,7 @@ def wrap_preformatted_span_with_table(main_tag, old_tag):
 
 
 def preprocess_pre_tags(chapter_tag):
-    """ Function preprocessing <pre> tags """
+    """Function preprocessing <pre> tags"""
     for pre in chapter_tag.find_all("pre"):
         new_tag = BeautifulSoup(features='lxml').new_tag("span")
         new_tag.attrs = pre.attrs.copy()
@@ -586,7 +593,7 @@ def preprocess_pre_tags(chapter_tag):
 
 
 def preprocess_code_tags(chapter_tag):
-    """ Function that emulates style of <code>, <kdb>, <var> """
+    """Function that emulates style of <code>, <kdb>, <var>"""
     for code in chapter_tag.find_all(re.compile("code|kdb|var")):
         code.name = 'span'
         if code.parent.name == "pre":
@@ -595,7 +602,7 @@ def preprocess_code_tags(chapter_tag):
 
 
 def prepare_title(title_of_chapter: str) -> str:
-    """ Function finalise processing/cleaning title """
+    """Function finalise processing/cleaning title"""
     title_str = BeautifulSoup(title_of_chapter, features='lxml').string
     title_str = re.sub(r'([\n\t\xa0])', ' ', title_str)
     title_str = re.sub(r' +', ' ', title_str).rstrip()
@@ -604,12 +611,27 @@ def prepare_title(title_of_chapter: str) -> str:
 
 
 def prepare_content(title_str: str, content_tag: BeautifulSoup, remove_title_from_chapter: bool) -> str:
-    """
-    Function finalise processing/cleaning content
+    """Function finalise processing/cleaning content
+    Parameters
+    ----------
+    title_str : str
+
+    content_tag : BeautifulSoup
+
+    remove_title_from_chapter : bool
+
+    Steps
+    ----------
     1. cleaning \n
     2. heading removal
     3. processing tags
     4. class removal
+
+    Returns
+    -------
+    str
+        Prepared content
+
     """
     # 0. cleaning \n
     to_remove = []