public RankingExpression transform(RankingExpression expression, RankProfileTransformContext context) {
        for (ExpressionTransformer transformer : transforms)
            expression = transformer.transform(expression, context);
        return expression;
    }
The transformations done on ranking expressions done at config time before passing them on to the Vespa
engine for execution.

An instance of this class has scope of a compilation of a single rank profile.

@author bratseth
config-model/src/main/java/com/yahoo/schema/expressiontransforms/ExpressionTransforms.java