code: def _register_tf_vjp():
      """
      Register the custom VJP for tensorflow
      """
      # pylint: disable=import-outside-toplevel
      import tensorflow as tf
  
      @tf.custom_gradient
      def _compute_fidelity_tf(dm0, dm1):
          fid = _compute_fidelity_vanilla(dm0, dm1)
  
          def vjp(grad_out):
              return _compute_fidelity_grad(dm0, dm1, grad_out)
  
          return fid, vjp
  
      ar.register_function(
          "tensorflow", "compute_fidelity", _compute_fidelity_tf
      )
  
file_path: pennylane/pennylane/math/fidelity.py
imports: from functools import lru_cache
  import autograd
  import autoray
  import pennylane
  from .utils import cast
  from .quantum import _check_density_matrix, _check_state_vector
label_desc: Use image node_id 13 for calling a global function with example usage: _register_tf_vjp() and returns: fid,  vjp, _compute_fidelity_grad