Abstract base class for the different types of expressions that can be used to create label text. Users can read the expression script using the LabelExpression.expression property. To specify an expression script, users create an object of type ArcadeLabelExpression, SimpleLabelExpression or WebmapLabelExpression with the required expression script and assign it to the label expression object.
The label expression script string. The expression is expected to be a complete, self-contained label expression in the language specified by the label expression subclass object. Warning: If the expression attempts to use attributes which don't exist then no label will be produced. This is distinct from the attribute existing but having a null or empty value, which can form part of the produced text label.