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"""Self Regularized Non-Monotonic Activation Function."""

import tensorflow as tf

from tensorflow_addons.utils import types


@tf.keras.utils.register_keras_serializable(package='Text')
def mish(x: types.TensorLike) -> tf.Tensor:
  """Mish activation function.

     Mish: A Self Regularized Non-Monotonic Activation Function
     https://arxiv.org/pdf/1908.08681.pdf

     Mish(x) = x * tanh(ln(1+e^x))

  Args:
    x: A `Tensor` representing preactivation values.

  Returns:
    The activation value.
  """
  x = tf.convert_to_tensor(x)
  return x * tf.tanh(tf.nn.softplus(x))
