code: def module_to_fqn(
      model: nn.Module, module: nn.Module, prefix: str = ""
  ) -> Optional[str]:
      """
      Returns the fqn for a module or None if module not a descendent of model.
      """
      if module is model:
          return ""
      for name, child in model.named_children():
          fqn = module_to_fqn(child, module, ".")
          if isinstance(fqn, str):
              return prefix + name + fqn
      return None
  
file_path: pytorch/torch/ao/pruning/sparsifier/utils.py
imports: from typing import Any, Dict, Optional, Type
  from torch.nn.utils.parametrize import type_before_parametrizations, is_parametrized
  from itertools import chain
  from torch import nn
label_desc: Use image node_id 3 for calling a global function with example usage: module_to_fqn(model, module, prefix) and returns: None, str, unknown