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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 _match_display_text(self, element_key, string, string_match_type, match):
 """Matches a display text value"""

        if string is None or string_match_type is None:
            raise NullArgument()
        match_value = self._get_string_match_value(string, string_match_type)
        self._add_match(element_key + '.text', match_value, match)