code: def find_in_line(line):  # type: (str) -> Optional[str]
      
      if not line:
          return None
  
      for method in [find_by_ast, find_version_by_string_lib, find_version_by_regex]:
          by = method(line)
          by = validate_string(by)
          if by:
              return by
      return None
docs: Find a version in a line.
      :param line:
      :return: