code: def is_semiconnected(G):
      r"""Returns True if the graph is semiconnected, False otherwise.
  
      A graph is semiconnected if and only if for any pair of nodes, either one
      is reachable from the other, or they are mutually reachable.
  
      This function uses a theorem that states that a DAG is semiconnected
      if for any topological sort, for node $v_n$ in that sort, there is an
      edge $(v_i, v_{i+1})$. That allows us to check if a non-DAG `G` is
      semiconnected by condensing the graph: i.e. constructing a new graph `H`
      with nodes being the strongly connected components of `G`, and edges
      (scc_1, scc_2) if there is a edge $(v_1, v_2)$ in `G` for some
      $v_1 \in scc_1$ and $v_2 \in scc_2$. That results in a DAG, so we compute
      the topological sort of `H` and check if for every $n$ there is an edge
      $(scc_n, scc_{n+1})$.
  
      Parameters
      ----------
      G : NetworkX graph
          A directed graph.
  
      Returns
      -------
      semiconnected : bool
          True if the graph is semiconnected, False otherwise.
  
      Raises
      ------
      NetworkXNotImplemented
          If the input graph is undirected.
  
      NetworkXPointlessConcept
          If the graph is empty.
  
      Examples
      --------
      >>> G = nx.path_graph(4, create_using=nx.DiGraph())
      >>> print(nx.is_semiconnected(G))
      True
      >>> G = nx.DiGraph([(1, 2), (3, 2)])
      >>> print(nx.is_semiconnected(G))
      False
  
      See Also
      --------
      is_strongly_connected
      is_weakly_connected
      is_connected
      is_biconnected
      """
      if len(G) == 0:
          raise nx.NetworkXPointlessConcept(
              "Connectivity is undefined for the null graph."
          )
  
      if not nx.is_weakly_connected(G):
          return False
  
      H = nx.condensation(G)
  
      return all(
          H.has_edge(u, v) for u, v in pairwise(nx.topological_sort(H))
      )
  
label_desc: Use image node_id 1 for calling a global function with example usage: is_semiconnected(G) and returns: all, False