Append the specified group of records to the sequence of groups maintained by this sample. If group.numRecords() is 0 this method has no effect. The behavior is undefined unless group.elapsedTime() > bsls::TimeInterval(0, 0). Note that the MetricRecord objects referred to by records are not copied: hence, the supplied array must remain valid for the productive lifetime of this object or until the group is removed by calling removeAllRecords().