code: def block_to_graph(block):
      """Convert a message flow graph (MFG) as a :class:`DGLBlock` object to a :class:`DGLGraph`.
  
      DGL will rename all the source node types by suffixing with ``_src``, and
      all the destination node types by suffixing with ``_dst``.
  
      Features on the returned graph will be preserved.
  
      Parameters
      ----------
      block : DGLBlock
          The MFG.
  
      Returns
      -------
      DGLGraph
          The graph.
  
      Examples
      --------
      >>> block = dgl.create_block({
      ...     ('A', 'AB', 'B'): ([1, 2, 3], [2, 1, 0]),
      ...     ('B', 'BA', 'A'): ([2, 1], [2, 3])})
      >>> g = dgl.block_to_graph(block)
      >>> g
      Graph(num_nodes={'A_src': 4, 'B_src': 3, 'A_dst': 4, 'B_dst': 3},
            num_edges={('A_src', 'AB', 'B_dst'): 3, ('B_src', 'BA', 'A_dst'): 2},
            metagraph=[('A_src', 'B_dst', 'AB'), ('B_src', 'A_dst', 'BA')])
      """
      new_types = [ntype + "_src" for ntype in block.srctypes] + [
          ntype + "_dst" for ntype in block.dsttypes
      ]
      retg = DGLGraph(block._graph, new_types, block.etypes)
  
      for srctype in block.srctypes:
          retg.nodes[srctype + "_src"].data.update(
              block.srcnodes[srctype].data
          )
      for dsttype in block.dsttypes:
          retg.nodes[dsttype + "_dst"].data.update(
              block.dstnodes[dsttype].data
          )
      for srctype, etype, dsttype in block.canonical_etypes:
          retg.edges[
              srctype + "_src", etype, dsttype + "_dst"
          ].data.update(block.edges[srctype, etype, dsttype].data)
  
      return retg
  
imports: from collections import defaultdict
  from collections.abc import Mapping
  import networkx
  import numpy
  from scipy.sparse import spmatrix
  from .None import backend, graph_index, heterograph_index, utils
  from .base import DGLError, EID, ETYPE, NID, NTYPE
  from .heterograph import combine_frames, DGLBlock, DGLGraph
label_desc: Use image node_id 5 for calling a global function with example usage: block_to_graph(block) and returns: retg