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# Copyright 2015 The TensorFlow Authors. All Rights Reserved.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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#     http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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# ==============================================================================
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"""A LazyLoader class."""
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from __future__ import absolute_import
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from __future__ import division
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import importlib
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import types
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class LazyLoader(types.ModuleType):
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  """Lazily import a module, mainly to avoid pulling in large dependencies.
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  `contrib`, and `ffmpeg` are examples of modules that are large and not always
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  needed, and this allows them to only be loaded when they are used.
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  """
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  # The lint error here is incorrect.
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  def __init__(self, local_name, parent_module_globals, name, warning=None):  # pylint: disable=super-on-old-class
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    self._local_name = local_name
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    self._parent_module_globals = parent_module_globals
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    self._warning = warning
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    super(LazyLoader, self).__init__(name)
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  def _load(self):
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    """Load the module and insert it into the parent's globals."""
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    # Import the target module and insert it into the parent's namespace
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    module = importlib.import_module(self.__name__)
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    self._parent_module_globals[self._local_name] = module
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    # Update this object's dict so that if someone keeps a reference to the
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    #   LazyLoader, lookups are efficient (__getattr__ is only called on lookups
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    #   that fail).
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    self.__dict__.update(module.__dict__)
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    return module
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  def __getattr__(self, item):
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    module = self._load()
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    return getattr(module, item)
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  def __dir__(self):
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    module = self._load()
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    return dir(module)