@Nonnull
  @ReturnsMutableCopy
  public ICommonsList <CSSViewportRule> getAllViewportRules ()
  {
    return m_aRules.getAllMapped (r -> r instanceof CSSViewportRule, r -> (CSSViewportRule) r);
  }
@ Nonnull @ ReturnsMutableCopy public ICommonsList < CSSViewportRule > getAllViewportRules ( ) { return m_aRules . getAllMapped ( r -> r instanceof CSSViewportRule , r -> ( CSSViewportRule ) r ) ; }
Get a list of all top-level rules that are viewport rules (implementing
{@link CSSViewportRule}).

@return A copy of all contained <code>@viewport</code> rules. Never
<code>null</code>.