code: def validate_namespace(ns: str) -> None:
      if "." in ns:
          raise ValueError(
              f'custom_op(..., ns="{ns}"): expected ns to not contain any . (and be a '
              f"valid variable name)"
          )
      if ns in RESERVED_NS:
          raise ValueError(
              f"custom_op(..., ns='{ns}'): '{ns}' is a reserved namespace, "
              f"please choose something else. "
          )
  
imports: import dataclasses
  import functools
  import inspect
  import sys
  import typing
  import weakref
  from torchgen.model import FunctionSchema, OperatorName, SchemaKind, BaseType, ListType, BaseTy
  import torch
  import torch._C
  import torch.library
  from torch._library.abstract_impl import AbstractImplCtx
  from torch.library import get_ctx
  from .autograd import autograd_kernel_indirection, construct_autograd_kernel
label_desc: Use image node_id 3 for calling a global function with example usage: validate_namespace(ns) without return types