def prepare_metadata_for_build_wheel(
        metadata_directory, config_settings, _allow_fallback):
    """Invoke optional prepare_metadata_for_build_wheel

    Implements a fallback by building a wheel if the hook isn't defined,
    unless _allow_fallback is False in which case HookMissing is raised.
    """
    backend = _build_backend()
    try:
        hook = backend.prepare_metadata_for_build_wheel
    except AttributeError:
        if not _allow_fallback:
            raise HookMissing()
        return _get_wheel_metadata_from_wheel(backend, metadata_directory,
                                              config_settings)
    else:
        return hook(metadata_directory, config_settings)
Invoke optional prepare_metadata_for_build_wheel

    Implements a fallback by building a wheel if the hook isn't defined,
    unless _allow_fallback is False in which case HookMissing is raised.
    
product/gradle-plugin/src/main/python/pip/_vendor/pep517/_in_process.py