code: def _to_4d(x):
      t = x  # Start with the original tensor
      while len(t.shape) < 4:  # Continue expanding dimensions until 4D
          t = tf.expand_dims(t, axis=0)
      return t
  
imports: import math
  from typing import Union, Optional, Tuple, List, Literal, Sequence, Callable
  import tensorflow
  from ivy.func_wrapper import inputs_to_ivy_arrays, output_to_native_arrays, with_unsupported_dtypes, with_supported_dtypes, with_supported_device_and_dtypes
  from ..None import backend_version
  import ivy
  from ivy.functional.ivy.layers import _handle_padding, _get_num_padded_values, _validate_max_pool_params, _depth_max_pooling_helper
  from ivy.functional.ivy.experimental.layers import _padding_ceil_mode, _get_size
label_desc: Use image node_id 48 for calling a global function with example usage: _to_4d(x) and returns: t