docs: def neighbors(self, node_id):
          """Find all the nodes where there is an edge from the specified node to that node.
          Returns a list of node ids."""
          node = self.get_node(node_id)
          flattened_nodes_list = []
          for a, b in [self.get_edge(edge_id)['vertices'] for edge_id in node['edges']]:
              flattened_nodes_list.append(a)
              flattened_nodes_list.append(b)
          node_set = set(flattened_nodes_list)
          if node_id in node_set:
              node_set.remove(node_id)
          return [nid for nid in node_set]