code: def is_variable(x):
      """
      An object is variable if it is either backend arrays or is a nested tuple
      containing at least one backend array.
      """
      return is_numeric_array(x)
  
file_path: funsor/funsor/ops/tracer.py
imports: from collections import OrderedDict
  from functools import singledispatch
  from .array import is_numeric_array
  from .op import trace_ops
  from .program import OpProgram
label_desc: Use image node_id 3 for calling a global function with example usage: is_variable(x) and returns: is_numeric_array