def METHOD_NAME(self, src_node, dest_node, edge_mod):
    """Adds edge to graph. Nodes added as well if they do not exist.
       Module which defines the edge must be provided for timing information."""
    src_node = src_node.lower()
    dest_node = dest_node.lower()
    self.graph[src_node].add(dest_node)
    self.edge_mods[(src_node, dest_node)] = edge_mod