Function exists

exists(expression): OGCCondition
Creates an "exists" expression. It evaluates to true if the value of the expression is defined.
```
  FilterFactory.exists( FilterFactory.property( "city_name" ) );

  FilterFactory.exists( FilterFactory.func( "getCityName" ) );
```
Parameters
- expression: Expression
  the expression to evaluate
Returns OGCCondition
the exists expression

Since
2022.1