code: public K removeValue(V _val) {
          checkParms(_val);
          K removedKey = inverseMap.remove(_val);
          if (removedKey != null) {
              map.remove(removedKey);
          }
          return removedKey;
      }
docs: Removes the mapping for a value from this map if it is present.
  
  @param _val value whose mapping is to be removed from the map
  @return the previous key associated with <tt>value</tt>.