code: def find_version_by_regex(file_source):  # type: (str)->Optional[str]
      
      if not file_source:
          return None
      version_match = re.search(r"^version=['\"]([^'\"]*)['\"]", file_source, re.M)
      if version_match:
          return version_match.group(1)
      return None
docs: Regex for dunder version