code: public static FieldCoordinates coordinates(String parentType, String fieldName) {
          assertValidName(parentType);
          assertValidName(fieldName);
          return new FieldCoordinates(parentType, fieldName);
      }
docs: Creates new field coordinates
  
  @param parentType the container of the field
  @param fieldName  the field name
  
  @return new field coordinates represented by the two parameters