public static ExtendedCell createFirstDeleteFamilyCellOnRow(final byte[] row, final byte[] fam) {
    return new FirstOnRowDeleteFamilyCell(row, fam);
  }
Create a Delete Family Cell for the specified row and family that would be smaller than all
other possible Delete Family KeyValues that have the same row and family. Used for seeking.
@param row - row key (arbitrary byte array)
@param fam - family name
@return First Delete Family possible key on passed <code>row</code>.
hbase-common/src/main/java/org/apache/hadoop/hbase/PrivateCellUtil.java