code: def isargument(self, node):
          
          try:
              node_id, _ = self.node_to_id(node)
              return (node_id in self.name_to_nodes and
                      any([isinstance(n, ast.Name) and
                           isinstance(n.ctx, ast.Param)
                           for n in self.name_to_nodes[node_id]]))
          except UnboundableRValue:
              return False
docs: checks whether node aliases to a parameter.