Get a comparison suffix to be used in Django ORM & inversion flag for it

        :param operator: string, DjangoQL comparison operator
        :return: (suffix, invert) - a tuple with 2 values:
            suffix - suffix to be used in ORM query, for example '__gt' for '>'
            invert - boolean, True if this comparison needs to be inverted

def get_operator(self, operator):
        """
        Get a comparison suffix to be used in Django ORM & inversion flag for it

        :param operator: string, DjangoQL comparison operator
        :return: (suffix, invert) - a tuple with 2 values:
            suffix - suffix to be used in ORM query, for example '__gt' for '>'
            invert - boolean, True if this comparison needs to be inverted
        """
        op = {
            '=': '',
            '>': '__gt',
            '>=': '__gte',
            '<': '__lt',
            '<=': '__lte',
            '~': '__icontains',
            'in': '__in',
        }.get(operator)
        if op is not None:
            return op, False
        op = {
            '!=': '',
            '!~': '__icontains',
            'not in': '__in',
        }[operator]
        return op, True