code: public BUILDER setAttributeGroup(String attributeGroup) {
          assert attributeGroup == null || attributeGroup.length() > 0;
          //noinspection deprecation
          this.attributeGroup = attributeGroup;
          return (BUILDER) this;
      }
docs: Sets the name of the attribute group with which this attribute is associated.
  
  @param attributeGroup the attribute group name. Cannot be an empty string but can be {@code null}
  if the attribute is not associated with a group.
  @return a builder that can be used to continue building the attribute definition