Returns a ``tuple`` of incoming edges for a **node object**.
        
        Arguments:
        
          - node(``object``) **node object** present in the graph to be queried 
            for incoming edges.

def incoming_edges(self, node):
        """
        Returns a ``tuple`` of incoming edges for a **node object**.
        
        Arguments:
        
          - node(``object``) **node object** present in the graph to be queried 
            for incoming edges.
          
        """
        edges = self.edges()
        in_edges = []
        for out_node, in_node in edges:
            if node is in_node:
                in_edges.append((out_node, in_node))
        return tuple(in_edges)