code: public boolean addFields(Collection<FormField> fieldsToAdd) {
          boolean fieldOverridden = false;
          synchronized (fields) {
              for (FormField field : fieldsToAdd) {
                  FormField previousField = fields.put(field.getVariable(), field);
                  if (previousField != null) {
                      fieldOverridden = true;
                  }
              }
          }
          return fieldOverridden;
      }
docs: Add the given fields to this form.
  
  @param fieldsToAdd
  @return true if a field was overridden.
  @since 4.3.0