code: def gelu(
      a: TensorLikeType, approximate: str = "none"
  ) -> TensorLikeType:
      """
      Reference implementation of torch.nn.functional.gelu
      """
      if not isinstance(a, TensorLike):
          raise RuntimeError(
              "Expected a tensor input for an elementwise unary operation!"
          )
      M_SQRT2 = 1.41421356237309504880
      M_SQRT1_2 = 0.70710678118654752440
      M_2_SQRTPI = 1.12837916709551257390
      if approximate == "tanh":
          kBeta = M_SQRT2 * M_2_SQRTPI * 0.5
          kKappa = 0.044715
          a_cube = a * a * a
          inner = kBeta * (a + kKappa * a_cube)
          return 0.5 * a * (1 + torch.tanh(inner))
      elif approximate == "none":
          kAlpha = M_SQRT1_2
          return a * 0.5 * (1 + torch.erf(a * kAlpha))
      else:
          raise RuntimeError(
              "approximate argument must be either none or tanh."
          )
  
imports: import math
  from functools import wraps
  from typing import Callable, Optional, Union
  import torch
  import torch._prims
  import torch._prims_common
  import torch._refs
  from torch._decomp import register_decomposition
  from torch._prims_common import ELEMENTWISE_TYPE_PROMOTION_KIND, NumberType, ShapeType, TensorLike, TensorLikeType
  from torch._prims_common.wrappers import elementwise_type_promotion_wrapper, elementwise_unary_scalar_wrapper, out_wrapper
  from torch._refs import _make_inplace
label_desc: Use image node_id 36 for calling a global function with example usage: gelu(a, approximate) and returns: unknown, unknown