private Object convertTimestamp(Object timestamp) {
        return convertTimestamp(timestamp, null);
    }
Convert the given timestamp to the target timestamp format.
@param timestamp the input timestamp, may be null
@param timestampFormat the format of the timestamp, or null if the format should be inferred
@return the converted timestamp
connect/transforms/src/main/java/org/apache/kafka/connect/transforms/TimestampConverter.java