code: def single_source_bellman_ford_path_length(
      G, source, weight="weight"
  ):
      """Compute the shortest path length between source and all other
      reachable nodes for a weighted graph.
  
      Parameters
      ----------
      G : NetworkX graph
  
      source : node label
          Starting node for path
  
      weight : string or function (default="weight")
          If this is a string, then edge weights will be accessed via the
          edge attribute with this key (that is, the weight of the edge
          joining `u` to `v` will be ``G.edges[u, v][weight]``). If no
          such edge attribute exists, the weight of the edge is assumed to
          be one.
  
          If this is a function, the weight of an edge is the value
          returned by the function. The function must accept exactly three
          positional arguments: the two endpoints of an edge and the
          dictionary of edge attributes for that edge. The function must
          return a number.
  
      Returns
      -------
      length : dictionary
          Dictionary of shortest path length keyed by target
  
      Raises
      ------
      NodeNotFound
          If `source` is not in `G`.
  
      Examples
      --------
      >>> G = nx.path_graph(5)
      >>> length = nx.single_source_bellman_ford_path_length(G, 0)
      >>> length[4]
      4
      >>> for node in [0, 1, 2, 3, 4]:
      ...     print(f"{node}: {length[node]}")
      0: 0
      1: 1
      2: 2
      3: 3
      4: 4
  
      Notes
      -----
      Edge weight attributes must be numerical.
      Distances are calculated as sums of weighted edges traversed.
  
      See Also
      --------
      single_source_dijkstra, single_source_bellman_ford
  
      """
      weight = _weight_function(G, weight)
      return _bellman_ford(G, [source], weight)
  
imports: from collections import deque
  from heapq import heappop, heappush
  from itertools import count
  import networkx
  from networkx.algorithms.shortest_paths.generic import _build_paths_from_predecessors
label_desc: Use image node_id 22 for calling a global function with example usage: single_source_bellman_ford_path_length(G, source, weight) and returns: _bellman_ford