code: def group_by(self, by=None, **additional_grouping_expressions):
          
          from ibis.expr.groupby import GroupedTableExpr
  
          return GroupedTableExpr(self, by, **additional_grouping_expressions)
docs: Create an intermediate grouped table expression, pending some group
          operation to be applied with it.
  
          Examples
          --------
          >>> import ibis
          >>> pairs = [('a', 'int32'), ('b', 'timestamp'), ('c', 'double')]
          >>> t = ibis.table(pairs)
          >>> b1, b2 = t.a, t.b
          >>> result = t.group_by([b1, b2]).aggregate(sum_of_c=t.c.sum())
  
          Notes
          -----
          group_by and groupby are equivalent, with `groupby` being provided for
          ease-of-use for pandas users.
  
          Returns
          -------
          grouped_expr : GroupedTableExpr