code: public boolean containsSimpleValue(V value) {
          for (List<V> vals : values()) {
              if ((vals.size() == 1) && vals.contains(value)) {
                  return true;
              }
          }
          return false;
      }
docs: Test for a specific single value in the map.
  <p>
  NOTE: This is a SLOW operation, and is actively discouraged.
  
  @param value the value to search for
  @return true if contains simple value