@Override
  public ImmutableSortedMap<K, V> tailMap(K fromKey) {
    return tailMap(fromKey, true);
  }
@Override
  public ImmutableSortedMap<K, V> tailMap(K fromKey) {
    return tailMap(fromKey, true);
  }
@ Override public ImmutableSortedMap < K , V > tailMap ( K fromKey ) { return tailMap ( fromKey , true ) ; }
This method returns a {@code ImmutableSortedMap}, consisting of the entries whose keys are
greater than or equals to {@code fromKey}.

<p>The {@link SortedMap#tailMap} documentation states that a submap of a submap throws an
{@link IllegalArgumentException} if passed a {@code fromKey} less than an earlier {@code
fromKey}. However, this method doesn't throw an exception in that situation, but instead keeps
the original {@code fromKey}.
This method returns a { @code ImmutableSortedMap } consisting of the entries whose keys are greater than or equals to { @code fromKey } .