code: def is_url(value):
      "Must start with http:// or https:// and contain JUST a URL"
      if not isinstance(value, str):
          return False
      if not value.startswith('http://') and not value.startswith('https://'):
          return False
      # Any whitespace at all is invalid
      if whitespace_re.search(value):
          return False
      return Truf is_url(value):
      "Must start with http:// or https:// and contain JUST a URL"
      if not isinstance(value, str):
          return False
      if not value.startswith('http://') and not value.startswith('https://'):
          return False
      # Any whitespace at all is invalid
      if whitespace_re.search(value):
          return False
      return True
docs: Must start with http:// or https:// and contain JUST a URL