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# Copyright (c) Facebook, Inc. and its affiliates.
""" Utilities for developers only.
These are not visible to users (not automatically imported). And should not
appeared in docs."""
# adapted from https://github.com/tensorpack/tensorpack/blob/master/tensorpack/utils/develop.py
def create_dummy_class(klass, dependency, message=""):
"""
When a dependency of a class is not available, create a dummy class which throws ImportError
when used.
Args:
klass (str): name of the class.
dependency (str): name of the dependency.
message: extra message to print
Returns:
class: a class object
"""
err = "Cannot import '{}', therefore '{}' is not available.".format(dependency, klass)
if message:
err = err + " " + message
class _DummyMetaClass(type):
# throw error on class attribute access
def __getattr__(_, __): # noqa: B902
raise ImportError(err)
class _Dummy(object, metaclass=_DummyMetaClass):
# throw error on constructor
def __init__(self, *args, **kwargs):
raise ImportError(err)
return _Dummy
def create_dummy_func(func, dependency, message=""):
"""
When a dependency of a function is not available, create a dummy function which throws
ImportError when used.
Args:
func (str): name of the function.
dependency (str or list[str]): name(s) of the dependency.
message: extra message to print
Returns:
function: a function object
"""
err = "Cannot import '{}', therefore '{}' is not available.".format(dependency, func)
if message:
err = err + " " + message
if isinstance(dependency, (list, tuple)):
dependency = ",".join(dependency)
def _dummy(*args, **kwargs):
raise ImportError(err)
return _dummy
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