code: def get_edge_ids_by_node_ids(self, node_a, node_b):
          
          # Check if the nodes are adjacent
          if not self.adjacent(node_a, node_b):
              return []
  
          # They're adjacent, so pull the list of edges from node_a and determine which ones point to node_b
          node = self.get_node(node_a)
          return [edge_id for edge_id in node['edges'] if self.get_edge(edge_id)['vertices'][1] == node_b]
docs: Returns a list of edge ids connecting node_a to node_b.