code: def create_anchor_from_header(header, existing_anchors=None):
      
      # Strip white space on the left/right and make lower case
      out = header.strip().lower()
  
      # Replace groups of white space with hyphens
      out = re.sub(r"\s+", lambda x: "-", out, flags=re.UNICODE)
  
      # Remove characters that aren't alphanumeric, hyphens, or spaces
      out = re.sub(r"[^\w\- ]+", lambda x: "", out, flags=re.UNICODE)
      if existing_anchors and out in existing_anchors.values():
          i = 1
          while (out + "-" + str(i)) in existing_anchors:
              i += 1
          return out + "-" + str(i)
      else:
          return out
docs: Creates GitHub style auto-generated anchor tags from header line strings
  
      :param header: The portion of the line that should be converted
      :param existing_anchors: A dictionary of AnchorHub tags to auto-generated
          anchors
      :return: A string auto-generated anchor in the GitHub format