将字符串解析为std :: time :: Duration 将字符串解析为Duration 。 字符串值单位支持以下之一: [y,mon,w,d,h,m,s] y:年。 支持字符串值: ["y" | "year" | "Y" | "YEAR" | "Year"] ["y" | "year" | "Y" | "YEAR" | "Year"] ["y" | "year" | "Y" | "YEAR" | "Year"] 。 例如1年 mon:Month.Support字符串值:`[“ mon” | “ MON” | “月” | “月” | “月”]。 例如1mon w:Week.Support字符串值: ["w" | "W" | "Week" | "WEEK" | "week"] ["w" | "W" | "Week" | "WEEK" | "week"] ["w" | "W" | "