code: def _signed_parabolic_tx(
      x: tf.Tensor, eps: float = 1e-3
  ) -> tf.Tensor:
      """Signed parabolic transform, inverse of signed_hyperbolic."""
      z = (
          tf.sqrt(1 + 4 * eps * (eps + 1 + abs(x))) / 2 / eps
          - 1 / 2 / eps
      )
      return tf.sign(x) * (tf.square(z) - 1)
  
file_path: acme/acme/tf/losses/r2d2.py
imports: from typing import Iterable, NamedTuple, Sequence
  import tensorflow
  import trfl
label_desc: Use image node_id 4 for calling a global function with example usage: _signed_parabolic_tx(x, eps) and returns: unknown