not() Operation of Boolean Expressions

not(<boolean expression>)
set aBoolean = anotherBoolean.not()

Negates the <boolean expression> or a boolean value.

anotherBoolean

Can be any variable or object attribute having the type Boolean. 

Returns false:

set inverted = not(true) 

Assigns the negation of the boolean value of x to y:

set y = x.not();