code: def desc(expr):
      
      if not isinstance(expr, Expr):
          return ops.DeferredSortKey(expr, ascending=False)
      else:
          return ops.SortKey(expr, ascending=False).to_expr()
docs: Create a sort key (when used in sort_by) by the passed array expression or
      column name.
  
      Parameters
      ----------
      expr : array expression or string
        Can be a column name in the table being sorted
  
      Examples
      --------
      >>> import ibis
      >>> t = ibis.table([('g', 'string')])
      >>> result = t.group_by('g').size('count').sort_by(ibis.desc('count'))