code: def shape(cls):
      return (len(cls.__args__),)
  
imports: import copyreg
  import functools
  import inspect
  import operator
  import warnings
  from functools import reduce
  from weakref import WeakValueDictionary
  import funsor.ops
  from funsor.ops.builtin import parse_ellipsis, parse_slice
  from funsor.util import broadcast_shape, get_backend, get_tracing_state, quote
label_desc: Use image node_id 4 for calling the ProductDomain obj's underlying member method code with example usage: obj.shape(cls) and returns: len