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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 set_secret_key(token):
 """ Initializes a Authentication and sets it as the new default global authentication. It also performs some checks before saving the authentication. :Example :param token: your secret token (live or sandbox) :type token: string """

    if not isinstance(token, string_types):
        raise exceptions.ConfigurationError('Expected string value for token.')

    config.secret_key = token