code: def calculate_concordance_by_annotation(graph, annotation, key, cutoff=None):
      
      return {
          value: calculate_concordance(subgraph, key, cutoff=cutoff)
          for value, subgraph in get_subgraphs_by_annotation(graph, annotation).items()
      }
docs: Returns the concordance scores for each stratified graph based on the given annotation
  
      :param pybel.BELGraph graph: A BEL graph
      :param str annotation: The annotation to group by.
      :param str key: The node data dictionary key storing the logFC
      :param float cutoff: The optional logFC cutoff for significance
      :rtype: dict[str,tuple]