code: def default(val, d):
      if exists(val):
          return val
      return d() if isfunction(d) else d
  
imports: import math
  from inspect import isfunction
  import numpy
  import paddle
  import paddle.nn
  import paddle.nn.functional
label_desc: Use image node_id 3 for calling a global function with example usage: default(val, d) and returns: unknown, val