function createFunctionCode(functionName, bodyLines, parameterNames = []) {
  const body = bodyLines.map(l => `  ${l}`).join('\n');
  const functionCode = `function ${functionName}(${parameterNames.join(', ')}) {\n${body}\n}`;
  return functionCode;
}
@param {string} functionName
@param {string[]} bodyLines
@param {string[]} parameterNames