code: def to_regex(regex, flags=0):
      
      if regex is None:
          raise TypeError('None can not be cast to re.RegexObject')
      if hasattr(regex, 'match'):
          return regex
      return re.compile(regex, flags)
docs: Given a string, this function returns a new re.RegexObject.
      Given a re.RegexObject, this function just returns the same object.
  
      :type  regex: string|re.RegexObject
      :param regex: A regex or a re.RegexObject
      :type  flags: int
      :param flags: See Python's re.compile().
      :rtype:  re.RegexObject
      :return: The Python regex object.