code: @Override
      public List<String> getMatchingPropIds(String searchKey)
              throws KnowledgeSourceReadException {
          LOGGER.log(Level.INFO,
                  "Searching knowledge source For search string {0}", searchKey);
          Set<String> searchResults = getSearchResultsFromBackend(searchKey);
          return new ArrayList<>(searchResults);
      }
docs: Gets the proposition Definitions from each backend that match the
  searchKey
  
  @param searchKey
  @return
  @throws KnowledgeSourceReadException