code: @Override
      public DefaultExceptionContext setContextValue(final String label, final Object value) {
          for (final Iterator<Pair<String, Object>> iter = contextValues.iterator(); iter.hasNext();) {
              final Pair<String, Object> p = iter.next();
              if (StringUtils.equals(label, p.getKey())) {
                  iter.remove();
              }
          }
          addContextValue(label, value);
          return this;
      }
docs: {@inheritDoc}