'Add an edge in the statement dependence graph from a program location `src` to another program location `dst`.
:param CodeLocation src: Source node.
:param CodeLocation dst: Destination node.
:param edge_labels: All labels associated with the edge.
:returns: None'

def _stmt_graph_add_edge(self, src, dst, **edge_labels):

    if ((src in self._stmt_graph) and (dst in self._stmt_graph[src])):
        return
    self._stmt_graph.add_edge(src, dst, **edge_labels)
