def fetch_cached_graph(rdf_url)
      statements = @client.get_statements(subject: rdf_url.to_s)
      if statements.count == 0
        puts "[INFO] fetch_cached_graph(#{rdf_url.to_s}) not found in triplestore cache (#{@client.url})"
        return nil
      end
      RDF::Graph.new.insert(*statements)
    end
def fetch_cached_graph(rdf_url)
      statements = @client.get_statements(subject: rdf_url.to_s)
      if statements.count == 0
        puts "[INFO] fetch_cached_graph(#{rdf_url.to_s}) not found in triplestore cache (#{@client.url})"
        return nil
      end
      RDF::Graph.new.insert(*statements)
    end
Fetch the graph from the triplestore cache

 @private
 @param [String] url
 @return [RDF::Graph] if the graph is found in the cache
 @return [nil] if the graph was not in the cache