code: def find_argname(self, argname, rec=False):
          
          if self.args:  # self.args may be None in some cases (builtin function)
              return _find_arg(argname, self.args, rec)
          return None, None
docs: Get the index and :class:`AssignName` node for given name.
  
          :param argname: The name of the argument to search for.
          :type argname: str
  
          :param rec: Whether or not to include arguments in unpacked tuples
              in the search.
          :type rec: bool
  
          :returns: The index and node for the argument.
          :rtype: tuple(str or None, AssignName or None)