def has_successor(self, u, v, t=None):
        """Return True if node u has successor v at time t (optional).

        This is true if graph has the edge u->v.

        Parameters
        ----------
        u, v : nodes
            Nodes can be, for example, strings or numbers.
            Nodes must be hashable (and not None) Python objects.
        t : snapshot id (default=None)
            If None will be returned the presence of the interaction on the flattened graph.

        """
        return self.has_interaction(u, v, t)
Return True if node u has successor v at time t (optional).

        This is true if graph has the edge u->v.

        Parameters
        ----------
        u, v : nodes
            Nodes can be, for example, strings or numbers.
            Nodes must be hashable (and not None) Python objects.
        t : snapshot id (default=None)
            If None will be returned the presence of the interaction on the flattened graph.