function connectionLineJs_(functionName, typeName) {
  var type = getOptTypesFrom(getRootBlock(), typeName);
  if (type) {
    type = ', ' + type;
  } else {
    type = '';
  }
  return '    this.' + functionName + '(true' + type + ');';
}
Create JS code required to create a top, bottom, or value connection.
@param {string} functionName JavaScript function name.
@param {string} typeName Name of type input.
@return {string} Line of JavaScript code to create connection.
@private