function getSignatureHelpItems(fileName, position) {
            synchronizeHostData();
            var sourceFile = getValidSourceFile(fileName);
            return ts.SignatureHelp.getSignatureHelpItems(program, sourceFile, position, cancellationToken);
        }
function getSignatureHelpItems(fileName, position) {
            synchronizeHostData();
            var sourceFile = getValidSourceFile(fileName);
            return ts.SignatureHelp.getSignatureHelpItems(program, sourceFile, position, cancellationToken);
        }
function getSignatureHelpItems ( fileName , position ) { synchronizeHostData ( ) ; var sourceFile = getValidSourceFile ( fileName ) ; return ts . SignatureHelp . getSignatureHelpItems ( program , sourceFile , position , cancellationToken ) ; }
Signature help 
This is a semantic operation.
Signature help This is a semantic operation .