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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 __get_value(self, field_name):

 """ Get request Json value by field name """

        value = request.values.get(field_name)
        if value is None:
            if self.json_form_data is None:
                value = None
            elif field_name in self.json_form_data:
                value = self.json_form_data[field_name]
        return value