code: @Nonnull
    public CSSMediaList addMedium (@Nonnull final ECSSMedium eMedium)
    {
      ValueEnforcer.notNull (eMedium, "Medium");
  
      m_aMedia.add (eMedium);
      return this;
    }
docs: Add a new medium to the list
  
  @param eMedium
  The medium to be added. May not be <code>null</code>.
  @return <code>this</code>