code: def _fileobj_to_fd(fileobj):
      
      if isinstance(fileobj, _INTEGER_TYPES):
          fd = fileobj
      else:
          for _integer_type in _INTEGER_TYPES:
              try:
                  fd = _integer_type(fileobj.fileno())
                  break
              except (AttributeError, TypeError, ValueError):
                  continue
          else:
              raise ValueError("Invalid file object: {0!r}".format(fileobj))
      if fd < 0:
          raise ValueError("Invalid file descriptor: {0}".format(fd))
      return fd
docs: Return a file descriptor from a file object. If
      given an integer will simply return that integer back.