docs: def siblings(self, node):
          """Returns all nodes that share the same parent (incoming node) with
          the given node, including the node itself.
          """
          incoming = self.incoming(node)
          # TODO: Not handling the case of multiple incoming nodes yet
          if len(incoming) == 1:
              incoming = incoming[0]
              siblings = self.outgoing(incoming)
              return siblings
          else:
              return [node]