code: static DoubleTuple createSubTuple(
          DoubleTuple parent, int fromIndex, int toIndex)
      {
          return new SubDoubleTuple(parent, fromIndex, toIndex);
      }
docs: Creates a new tuple that is a <i>view</i>
  on the specified portion of the given parent. Changes in the
  parent will be visible in the returned tuple.
  
  @param parent The parent tuple
  @param fromIndex The start index in the parent, inclusive
  @param toIndex The end index in the parent, exclusive
  @throws NullPointerException If the given parent is <code>null</code>
  @throws IllegalArgumentException If the given indices are invalid.
  This is the case when <code>fromIndex &lt; 0</code>,
  <code>fromIndex &gt; toIndex</code>, or
  <code>toIndex &gt; {@link Tuple#getSize() parent.getSize()}</code>,
  @return The new tuple