'Add borders to table. This is called from self._balance.'

def _borders(self):

    (nx, ny) = ((self.ncols - 1), (self.nrows - 1))
    options = self.options
    for (ix, col) in enumerate(self.worktable):
        for (iy, cell) in enumerate(col):
            col.reformat_cell(iy, **self._cellborders(ix, iy, nx, ny, **options))
