code: public PoolDeleteOptions withIfModifiedSince(DateTime ifModifiedSince) {
          if (ifModifiedSince == null) {
              this.ifModifiedSince = null;
          } else {
              this.ifModifiedSince = new DateTimeRfc1123(ifModifiedSince);
          }
          return this;
      }
docs: Set a timestamp indicating the last modified time of the resource known to the client. The operation will be performed only if the resource on the service has been modified since the specified time.
  
  @param ifModifiedSince the ifModifiedSince value to set
  @return the PoolDeleteOptions object itself.