code: @Override
      public String getHeader(String header) {
          if (isSystemBundleProvider) {
              if (FeatureDefinitionUtils.IBM_API_PACKAGE.equals(header))
                  return generateHeaderFromDefinitions("IBM-MergedApiPackage", sysPkgApiHeader);
              if (FeatureDefinitionUtils.IBM_SPI_PACKAGE.equals(header))
                  return generateHeaderFromDefinitions("IBM-MergedSpiPackage", sysPkgSpiHeader);
          }
          return super.getHeader(header);
      }
docs: /*
  (non-Javadoc)
  
  @see com.ibm.ws.kernel.feature.internal.subsystem.SubsystemFeatureDefinitionImpl#getHeader(java.lang.String)