code: public final SgField findFieldByName(final String name) {
          if (name == null) {
              throw new IllegalArgumentException("The argument 'name' cannot be null!");
          }
          for (int i = 0; i < fields.size(); i++) {
              final SgField field = fields.get(i);
              if (field.getName().equals(name)) {
                  return field;
              }
          }
          return null;
      }
docs: Find a field by it's name.
  
  @param name
  Name of the field to find - Cannot be null.
  
  @return Field or null if it's not found.