code: def to_tf_signature(signature):
      """
      Converts a Dataset signature to a TensorFlow signature.
      :param signature: a Dataset signature.
      :return: a TensorFlow signature.
      """
      output = []
      keys = ["x", "a", "e", "i"]
      for k in keys:
          if k in signature:
              shape = signature[k]["shape"]
              dtype = signature[k]["dtype"]
              spec = signature[k]["spec"]
              output.append(spec(shape, dtype))
      output = tuple(output)
      if "y" in signature:
          shape = signature["y"]["shape"]
          dtype = signature["y"]["dtype"]
          spec = signature["y"]["spec"]
          output = (output, spec(shape, dtype))
  
      return output
  
file_path: spektral/spektral/data/utils.py
imports: import numpy
  import tensorflow
  from scipy import sparse
  from spektral.utils import pad_jagged_array
  from spektral.utils.sparse import sp_matrix_to_sp_tensor
label_desc: Use image node_id 8 for calling a global function with example usage: to_tf_signature(signature) and returns: output