code: public CmsJspDateSeriesBean getParentSeries() {
  
          if ((m_parentSeries == null) && getIsExtractedDate()) {
              CmsObject cms = m_value.getCmsObject();
              try {
                  CmsResource res = cms.readResource(m_seriesDefinition.getParentSeriesId());
                  CmsJspContentAccessBean content = new CmsJspContentAccessBean(cms, m_value.getLocale(), res);
                  CmsJspContentAccessValueWrapper value = content.getValue().get(m_value.getPath());
                  return new CmsJspDateSeriesBean(value, m_locale);
              } catch (NullPointerException | CmsException e) {
                  LOG.warn("Parent series with id " + m_seriesDefinition.getParentSeriesId() + " could not be read.", e);
              }
  
          }
          return null;
      }
docs: Returns the parent series, if it is present, otherwise <code>null</code>.<p>
  
  @return the parent series, if it is present, otherwise <code>null</code>