code: def by_chat_command(prefix=('/',), separator=' ', pass_args=False):
      
      return by_command(lambda msg: msg['text'], prefix, separator, pass_args)
docs: :param prefix:
          a list of special characters expected to indicate the head of a command.
  
      :param separator:
          a command may be followed by arguments separated by ``separator``.
  
      :type pass_args: bool
      :param pass_args:
          If ``True``, arguments following a command will be passed to the handler
          function.
  
      :return:
          a key function that interprets a chat message's text and returns
          the embedded command, optionally followed by arguments. If the text is
          not preceded by any of the specified ``prefix``, it returns a 1-tuple
          ``(None,)`` as the key. This is to distinguish with the special
          ``None`` key in routing table.