code: public static void clearEvidence(Network bn, String nodeName)
              throws ShanksException {
          int node = bn.getNode(nodeName);
          if (bn.isEvidence(node)) {
              bn.clearEvidence(nodeName);
              bn.updateBeliefs();
          }
      }
docs: Clear a hard evidence fixed in a given node
  
  /**
  
  @param bn
  @param nodeName
  @throws ShanksException