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# contributor license agreements. See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You 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,
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# limitations under the License.

from torch import nn


class LossKey:
    BCELoss = "BCELoss".lower()
    CrossEntropyLoss = "CrossEntropyLoss".lower()
    NLLLoss = "NLLLoss".lower()
    BCEWithLogitsLoss = "BCEWithLogitsLoss".lower()


def get_loss_fn(key: str):
    key = key.lower()
    if key == LossKey.BCELoss:
        return nn.BCELoss
    if key == LossKey.BCEWithLogitsLoss:
        return nn.BCEWithLogitsLoss
    if key == LossKey.CrossEntropyLoss:
        return nn.CrossEntropyLoss
    if key == LossKey.NLLLoss:
        return nn.NLLLoss
    raise ValueError("Invalid loss_key:", key)
