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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 process_alias_export_namespace(namespace):
 """ Validate input arguments when the user invokes 'az alias export'. Args: namespace: argparse namespace object. """

    namespace.export_path = os.path.abspath(namespace.export_path)
    if os.path.isfile(namespace.export_path):
        raise CLIError(FILE_ALREADY_EXISTS_ERROR.format(namespace.export_path))

    export_path_dir = os.path.dirname(namespace.export_path)
    if not os.path.isdir(export_path_dir):
        os.makedirs(export_path_dir)

    if os.path.isdir(namespace.export_path):
        namespace.export_path = os.path.join(namespace.export_path, ALIAS_FILE_NAME)