def __str__(self):
        """
        Pretty print dialogue Act Item.

        :return: string
        """

        opr = 'UNK'
        if self.op == Operator.EQ:
            opr = '='
        elif self.op == Operator.NE:
            opr = '!='
        elif self.op == Operator.LT:
            opr = '<'
        elif self.op == Operator.LE:
            opr = '<='
        elif self.op == Operator.GT:
            opr = '>'
        elif self.op == Operator.GE:
            opr = '>='
        elif self.op == Operator.AND:
            opr = 'AND'
        elif self.op == Operator.OR:
            opr = 'OR'
        elif self.op == Operator.NOT:
            opr = 'NOT'
        elif self.op == Operator.IN:
            opr = 'IN'

        result = self.slot

        if self.value:
            result += ' ' + opr + ' ' + self.value

        return result

        Pretty print dialogue Act Item.

        :return: string
        
plato/dialogue/action.py