code: def is_f_connected(H, source_node, target_node):
      
      f_visited_nodes, Pv, Pe, v = f_visit(H, source_node)
      return target_node in f_visited_nodes
docs: Checks if a target node is F-connected to a source node.
  
      A node t is F-connected to a node s iff s if B-connected to t.
      Refer to 'f_visit's or 'is_b_connected's documentation for more details.
  
      :param H: the hypergraph to check F-connectedness on.
      :param source_node: the node to check F-connectedness to.
      :param target_node: the node to check F-connectedness of.
      :returns: bool -- whether target_node can be visited from source_node.