code: public static ProfileField<?>[] fromIdentifierList(String[] identifiers) {
  		if (identifiers == null) {
  			return null;
  		}
  
  		ProfileField<?>[] fields = new ProfileField<?>[identifiers.length];
  		for (int i = 0; i < identifiers.length; i++) {
  			fields[i] = lookup(identifiers[i]);
  
  			if (fields[i] == null) {
  				throw new IllegalArgumentException("Unknown field " + identifiers[i]);
  			}
  		}
  
  		return fields;
  	}
docs: Converts an array of profile field identifier to an array of
  {@link ProfileField}
  
  @param identifiers
  the array of identifier
  @return the converted array of {@link ProfileField}