Override portrait option from children class a0poster

I would like to override the options portrait line in the line 15 for use with landscape.

documentclass{modernposter}
%Something like documentclass[landscape]{modernposter}

title{This is a Modernposter Demo}
author{Firstname Lastname}
email{[email protected]} 

begin{document}
  maketitle  

  begin{postercolumn}
    posterbox{Introduction}{ 
      $dots$
    }
  end{postercolumn} 
  begin{postercolumn}
    doubleposterbox[0.6]
      {Problem Statement}{
        $dots$
      }
      {highlight{Results}}{ 
        $dots$
      }
  end{postercolumn}
end{document}