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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 _check_not_empty(string):
 """ Checks that the string is not empty. If it is empty an exception is raised, stopping the validation. This is used for compulsory alphanumeric fields. :param string: the field value """

    string = string.strip()

    if len(string) == 0:
        message = 'The string should not be empty'
        raise pp.ParseException(message)