public boolean has(byte[] family, byte[] qualifier, long ts) {
    return has(family, qualifier, ts, HConstants.EMPTY_BYTE_ARRAY, false, true);
  }
A convenience method to determine if this object's familyMap contains a value assigned to the
given family, qualifier and timestamp. All 3 given arguments must match the KeyValue object to
return true.
@param family    column family
@param qualifier column qualifier
@param ts        timestamp
@return returns true if the given family, qualifier and timestamp already has an existing
        KeyValue object in the family map.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/Mutation.java