def edge_cost(self, node_a, node_b):
cost = float('<STR_LIT>')<EOL>node_object_a = self.get_node(node_a)<EOL>for edge_id in node_object_a['<STR_LIT>']:<EOL><INDENT>edge = self.get_edge(edge_id)<EOL>tpl = (node_a, node_b)<EOL>if edge['<STR_LIT>'] == tpl:<EOL><INDENT>cost = edge['<STR_LIT>']<EOL>break<EOL><DEDENT><DEDENT>return cost<EOL>
Returns the cost of moving between the edge that connects node_a to node_b.
        Returns +inf if no such edge exists.