def get_group_by_class(self, definition):
group_by = definition["<STR_LIT>"]<EOL>series = definition["<STR_LIT>"]<EOL>if "<STR_LIT>" in definition:<EOL><INDENT>formatter = {group_by: definition["<STR_LIT>"]}<EOL><DEDENT>else:<EOL><INDENT>formatter = {}<EOL><DEDENT>return self.ProcessClass([group_by], series, formatter)<EOL>
intantiates the processing class (Direct or Grouped) and returns it.