# Copyright 2024 The AI Edge Model Explorer Authors.
#
# 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.
# ==============================================================================


class Singleton(type):
  """A metaclass for setting a class as singleton."""

  def __init__(cls, name, bases, dict):
    super(Singleton, cls).__init__(name, bases, dict)
    cls.instance = None

  def __call__(cls, *args, **kw):
    if cls.instance is None:
      cls.instance = super(Singleton, cls).__call__(*args, **kw)
    return cls.instance
