whole_func_string: function indentStr(str: string, indent: number): string {
    let result = ''
    for (let index = 0; index < indent; index++) result += '  '
    return result + str
  }
func_code_string: function indentStr(str: string, indent: number): string {
    let result = ''
    for (let index = 0; index < indent; index++) result += '  '
    return result + str
  }
func_documentation_string: Indent a string.
  http://jsperf.com/array-join-vs-for