code: def group_by(self, *args, **kwds):
          
          self._group_by.group_by(*args, **kwds)
          return self
docs: Default ordering is ``ASC``.
  
          ``group_by`` accept ``dict`` as you would expect, but note that ``dict``
          does not have same order. Same for named arguments.
  
          .. code-block:: python
  
              >>> sqlpuzzle.select('c').from_('t').group_by('a', ('b', 'desc'))
              <Select: SELECT "c" FROM "t" GROUP BY "a", "b" DESC>