code: public Rowtime timestampsFromField(String fieldName) {
  		internalProperties.putString(ROWTIME_TIMESTAMPS_TYPE, ROWTIME_TIMESTAMPS_TYPE_VALUE_FROM_FIELD);
  		internalProperties.putString(ROWTIME_TIMESTAMPS_FROM, fieldName);
  		return this;
  	}
docs: Sets a built-in timestamp extractor that converts an existing {@link Long} or
  {@link Types#SQL_TIMESTAMP} field into the rowtime attribute.
  
  @param fieldName The field to convert into a rowtime attribute.