'Implements the del [] operator. Used to remove filters.'

def __delitem__(self, filter):

    dict.__delitem__(self, filter)
    del self.__filter_order[filter]
    match = Query.FILTER_REGEX.match(filter)
    property = match.group(1)
    operator = match.group(3)
    if (operator in self.INEQUALITY_OPERATORS):
        assert (self.__inequality_count >= 1)
        assert (property == self.__inequality_prop)
        self.__inequality_count -= 1
        if (self.__inequality_count == 0):
            self.__inequality_prop = None
