code: def _get_activation_fn(activation):
      """Return an activation function given a string"""
      if activation == "relu":
          return F.relu
      if activation == "gelu":
          return F.gelu
      if activation == "glu":
          return F.glu
      raise RuntimeError(
          f"activation should be relu/gelu, not {activation}."
      )
  
imports: import math
  import torch
  from torch import nn, Tensor
  import torch.nn.functional
  from typing import Optional
  from modules.codeformer.vqgan_arch import VQAutoEncoder, ResBlock
  from basicsr.utils.registry import ARCH_REGISTRY
label_desc: Use image node_id 3 for calling a global function with example usage: _get_activation_fn(activation) and returns: F, F, F