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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _get_explicit_environ_credentials():
 """Gets credentials from the GOOGLE_APPLICATION_CREDENTIALS environment variable."""

    explicit_file = os.environ.get(environment_vars.CREDENTIALS)

    if explicit_file is not None:
        credentials, project_id = _load_credentials_from_file(
            os.environ[environment_vars.CREDENTIALS])

        return credentials, project_id

    else:
        return None, None