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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 _normalize_method_name(method):
 """ Returns a lower case, normalized version of HTTP Method. It also know how to handle API Gateway specific methods like "ANY" NOTE: Always normalize before using the `method` value passed in as input :param string method: Name of the HTTP Method :return string: Normalized method name """

        if not method or not isinstance(method, string_types):
            return method

        method = method.lower()
        if method == 'any':
            return SwaggerEditor._X_ANY_METHOD
        else:
            return method