docs: private EightyFS checkProviderAndGet80( @Nullable Path path ) {
          if( path == null ) {
              throw new IllegalArgumentException( "argument was null" );
          }
  
          if( path.getFileSystem().provider() != this ) {
              throw new ProviderMismatchException( "expected path for " + getScheme() + " got " + path.getFileSystem().provider().getScheme() );
          }
  
          if( !path.getFileSystem().isOpen() ) {
              throw new ClosedFileSystemException();
          }
  
          return ( (EightyFileSystem) path.getFileSystem() ).get80();
      }