code: def __getitem__(cls, arg_domains):
      try:
          return ProductDomain._type_cache[arg_domains]
      except KeyError:
          assert isinstance(arg_domains, tuple)
          assert all(
              isinstance(arg_domain, Domain)
              for arg_domain in arg_domains
          )
          subcls = type(
              "Product_", (Product,), {"__args__": arg_domains}
          )
          ProductDomain._type_cache[arg_domains] = subcls
          return subcls
  
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 1 for calling the ProductDomain obj's underlying member method code with example usage: obj.__getitem__(cls, arg_domains) and returns: ProductDomain, subcls