code: def _iter_module_files():
      
      # The list call is necessary on Python 3 in case the module
      # dictionary modifies during iteration.
      for module in list(sys.modules.values()):
          if module is None:
              continue
          filename = getattr(module, "__file__", None)
          if filename:
              if os.path.isdir(filename) and os.path.exists(
                  os.path.join(filename, "__init__.py")
              ):
                  filename = os.path.join(filename, "__init__.py")
  
              old = None
              while not os.path.isfile(filename):
                  old = filename
                  filename = os.path.dirname(filename)
                  if filename == old:
                      break
              else:
                  if filename[-4:] in (".pyc", ".pyo"):
                      filename = filename[:-1]
                  yield filename
docs: This iterates over all relevant Python files.  It goes through all
      loaded files from modules, all files in folders of already loaded modules
      as well as all files reachable through a package.