code: def is_zpk(zpktup):
      
      return (
          isinstance(zpktup, (tuple, list)) and
          len(zpktup) == 3 and
          isinstance(zpktup[0], (list, tuple, numpy.ndarray)) and
          isinstance(zpktup[1], (list, tuple, numpy.ndarray)) and
          isinstance(zpktup[2], float))
docs: Determin whether the given tuple is a ZPK-format filter definition
  
      Returns
      -------
      iszpk : `bool`
          `True` if the ``zpktup`` looks like a ZPK-format filter definition,
          otherwise `False`