docs: def connect_from(self, vertex, weight=1):
          """
          Connect another vertex to this one.
  
          Args:
              vertex (Vertex): vertex to connect from.
              weight (int): weight of the edge.
  
          Returns:
              Edge: the newly created edge.
          """
          for edge in self.edges_in:
              if vertex == edge.vertex_out:
                  return edge
          return Edge(vertex, self, weight)