code: public static Map<String, String> getEvidences(Network bn) {
  
          HashMap<String, String> evidences = new HashMap<String, String>();
          for (int n : bn.getAllNodes()) {
              if (bn.isEvidence(n)) {
                  evidences.put(bn.getNodeName(n), bn.getEvidenceId(n));
              }
          }
          return evidences;
      }
docs: Return all current evidences in the BN
  
  @param bn
  @return