code: def generate_bioprocess_mechanisms(graph, key: Optional[str] = None) -> Mapping[BiologicalProcess, BELGraph]:
      
      return {
          biological_process: generate_mechanism(graph, biological_process, key=key)
          for biological_process in get_nodes_by_function(graph, BIOPROCESS)
      }
docs: Generate a mechanistic sub-graph for each biological process in the graph using :func:`generate_mechanism`.
  
      :param graph: A BEL graph
      :param key: The key in the node data dictionary representing the experimental data.