code: private void assertAttributeExists(String attribute) throws UnknownColumnException {
  		for (DataColumn column : columns) {
  			if (column.getCode().equals(attribute)) {
  				return;
  			}
  		}
  		throw new UnknownColumnException(attribute);
  	}
docs: Asserts that the given attribute exists as a column in this table.
  
  @param attribute the attribute to find
  @throws UnknownColumnException if the attribute doesn't exist