public boolean isSet(_Fields field) {
    if (field == null) {
      throw new java.lang.IllegalArgumentException();
    }

    switch (field) {
    case IS_DELETE:
      return isSetIsDelete();
    case COLUMN:
      return isSetColumn();
    case VALUE:
      return isSetValue();
    case WRITE_TO_WAL:
      return isSetWriteToWAL();
    }
    throw new java.lang.IllegalStateException();
  }
Returns true if field corresponding to fieldID is set (has been assigned a value) and false otherwise
hbase-thrift/src/main/java/org/apache/hadoop/hbase/thrift/generated/Mutation.java