code: public Date get(String name) throws IOException {
          if (name.equalsIgnoreCase(NOT_BEFORE)) {
              return (getNotBefore());
          } else if (name.equalsIgnoreCase(NOT_AFTER)) {
              return (getNotAfter());
          } else {
              throw new IOException("Attribute name not recognized by " +
                              "CertAttrSet: CertificateValidity.");
          }
      }
docs: Get the attribute value.