code: def tv_to_tensor(value, dtype=None, name=None, as_ref=None):
      """Converts a TensorVariable to a tf.Tensor."""
      del as_ref
      tensor_value = value.tensor_value
      if tensor_value is None:
          # TODO(tomhennigan) We should probably not notify in this case.
          tensor_value = tf.zeros(value.shape, dtype=value.dtype)
      if dtype is not None:
          tensor_value = tf.cast(tensor_value, dtype=dtype, name=name)
      return tensor_value
  
imports: import collections
  import functools
  import itertools
  import threading
  import contextlib
  from sonnet.src.functional import utils
  import tensorflow
label_desc: Use image node_id 8 for calling a global function with example usage: tv_to_tensor(value, dtype, name, as_ref) and returns: tensor_value