code: def return_type_str_pyi(t: Type) -> str:
      # Where arguments are open to accepting Union, return types should return
      # concrete types
  
      if isinstance(t, OptionalType):
          inner = return_type_str_pyi(t.elem)
          return f"Optional[{inner}]"
  
      if isinstance(t, BaseType):
          if t.name == BaseTy.Device:
              return "_device"
          elif t.name == BaseTy.Dimname:
              ret = "Optional[str]"
          else:
              return argument_type_str_pyi(t)
  
      if isinstance(t, ListType):
          inner = return_type_str_pyi(t.elem)
          return f"List[{inner}]"
  
      return argument_type_str_pyi(t)
  
imports: from dataclasses import dataclass
  from typing import Dict, List, Optional, Sequence, Set, Tuple, Union
  from torchgen.api import cpp
  from torchgen.api.types import Binding, CppSignature, CppSignatureGroup
  from torchgen.gen import pythonify_default
  from torchgen.model import Argument, BaseTy, BaseType, FunctionSchema, ListType, NativeFunction, OptionalType, Return, Type, Variant
label_desc: Use image node_id 10 for calling a global function with example usage: return_type_str_pyi(t) and returns: argument_type_str_pyi, str, inner, str, str, inner, str, str, argument_type_str_pyi