code: public static String[] toIdentifierList(ProfileField<?>[] fields) {
  		if (fields == null) {
  			return null;
  		}
  
  		String[] identifiers = new String[fields.length];
  		for (int i = 0; i < fields.length; i++) {
  			identifiers[i] = fields[i].getIdentifier();
  		}
  
  		return identifiers;
  	}
docs: Converts an array of {@link ProfileField} to an array of String,
  containing the identifier of the original fields, in the same order.
  
  @param fields
  - the array to convert
  @return the array of identifiers