# Copyright 2019 DeepMind Technologies Limited. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# ==============================================================================
"""Base types for the second order sub-package."""

import abc
from typing import Any, Protocol

import jax


class LossFn(Protocol):
  """A loss function to be optimized."""

  @abc.abstractmethod
  def __call__(
      self, params: Any, inputs: jax.Array, targets: jax.Array
  ) -> jax.Array:
    ...
