code: @Override
      public Object put(final String key, final Object v) {
          return put(_getInt(key), v);
      }
docs: Puts a value at an index. For interface compatibility.  Must be passed a String that is parsable to an int.
  
  @param key the index at which to insert the value
  @param v   the value to insert
  @return the value
  @throws IllegalArgumentException if {@code key} cannot be parsed into an {@code int}