code: def exists(val):
      return val is not None
  
imports: import math
  from inspect import isfunction
  import torch
  import torch.nn.functional
  from apex.contrib.group_norm import GroupNorm
  from einops import rearrange
  from torch import einsum, nn
  from torch._dynamo import disable
  from nemo.collections.multimodal.modules.stable_diffusion.diffusionmodules.util import checkpoint
label_desc: Use image node_id 2 for calling a global function with example usage: exists(val) and returns: unknown