Filter
        Performs value filtering and returns filtered result.

        :param value:           input value
        :param model:           parent model being validated
        :param context:         object, filtering context
        :return:                filtered value

def filter(self, value, model=None, context=None):
        """
        Filter
        Performs value filtering and returns filtered result.

        :param value:           input value
        :param model:           parent model being validated
        :param context:         object, filtering context
        :return:                filtered value
        """

        value = str(value)
        pattern = r'\d+'
        found = ''.join(re.findall(pattern, value))

        if found and self.to_int:
            found = int(found)

        return found