code: @Override
      public void include(Readable in, String source) throws IOException
      {
          if (cursor != end)
          {
              release();
          }
          if (includeStack == null)
          {
              includeStack = new ArrayDeque<>();
          }
          includeStack.push(includeLevel);
          includeLevel = new IncludeLevel(in, source);
      }
docs: Include Readable at current input. Readable is read as part of
  input. When Readable ends, input continues using current input.
  
  <p>Included reader is closed at eof
  
  @param in
  @param source
  @throws IOException