Object (@NotNull PyPrefixExpression expression) { if (expression.getOperator() == PyTokenTypes.NOT_KEYWORD) { final Boolean value = PyUtil.as(evaluate(expression.getOperand()), Boolean.class); if (value != null) { return !value; } } else if (expression.getOperator() == PyTokenTypes.MINUS) { final Number number = PyUtil.as(evaluate(expression.getOperand()), Number.class); if (number != null) { return fromBigInteger(toBigInteger(number).negate()); } } return null; }