parameters: (self, groupby_str)
docstring: Parse a line that represent 'group by' clause.
docstring_summary: Parse a line that represent 'group by' clause.
docstring_tokens: Parse a line that represent group by clause .
function: def parse_groupby(self, groupby_str):
      """Parse a line that represent 'group by' clause."""
      v_id = self.plan_stack[-1].id
      self.groupby[v_id] = groupby_str
function_tokens: def parse_groupby ( self , groupby_str ) : v_id = self . plan_stack [ - 1 ] . id self . groupby [ v_id ] = groupby_str