Outputs this period as a {@code string}, such as {@code P6Y3M1D}. !(p) The output will be _in the ISO-8601 period format. A zero period will be represented as zero days, 'P0D'.
@return a string representation of this period, not null
See Implementation
Outputs this period as a {@code string}, such as {@code P6Y3M1D}. !(p) The output will be _in the ISO-8601 period format. A zero period will be represented as zero days, 'P0D'.
@return a string representation of this period, not null