def reverse_complement( self ):
        """
        Create the reverse complement of this matrix. The result probably
        only makese sense if the alphabet is that of DNA ('A','C','G','T').
        """
        rval = copy( self )
        # Conveniently enough, reversing rows and columns is exactly what we
        # want, since this results in A swapping with T and C swapping with G.
        rval.values = self.values[::-1,::-1].copy()
        return rval