@Override
    public void process(boolean validate, boolean documentsOnly) {
        if ( ! validate) return;
        if (documentsOnly) return;

        for (RankProfile rp : rankProfileRegistry.all()) {
            for (String functionName : rp.getFunctions().keySet()) {
                if (reservedNames.contains(functionName)) {
                    deployLogger.logApplicationPackage(Level.WARNING, "Function '" + functionName + "' " +
                                                                      "in rank profile '" + rp.name() + "' " +
                                                                      "has a reserved name. This might mean that the function shadows " +
                                                                      "the built-in function with the same name."
                    );
                }
            }
        }
    }
Issues a warning if some function has a reserved name. This is not necessarily
an error, as a rank profile function can shadow a built-in function.

@author lesters
config-model/src/main/java/com/yahoo/schema/processing/ReservedFunctionNames.java