code: def is_variable(t: TensorData) -> bool:
      """
      Returns whether the `t` is a TensorFlow variable.
      """
      return isinstance(t, (tf.Variable, tfp.util.TransformedVariable))
  
file_path: GPflow/gpflow/utilities/misc.py
imports: from typing import Callable, Iterable, List, Optional, Union
  import tensorflow
  import tensorflow_probability
  from check_shapes import check_shapes
  from ..base import TensorData
  from ..config import default_float, default_int
label_desc: Use image node_id 4 for calling a global function with example usage: is_variable(t) and returns: isinstance