public boolean has(byte[] family, byte[] qualifier, long ts, byte[] value) {
    return has(family, qualifier, ts, value, false, false);
  }
A convenience method to determine if this object's familyMap contains the given value assigned
to the given family, qualifier and timestamp. All 4 given arguments must match the KeyValue
object to return true.
@param family    column family
@param qualifier column qualifier
@param ts        timestamp
@param value     value to check
@return returns true if the given family, qualifier timestamp and value already has an existing
        KeyValue object in the family map.
hbase-client/src/main/java/org/apache/hadoop/hbase/client/Mutation.java