protected FunctionSignature[] getFunctionSignatures() {
FunctionSignature fs = new FunctionSignature( 3 );
// message
fs.addParam( String.class, true );
// choices
fs.addParam( Scriptable.class, true );
// callback
fs.addParam( ScriptableFunction.class, true );
// filler
fs.addParam( Object.class, false );
return new FunctionSignature[] { fs };