code: def get_all_dbparameters(self, groupname, source=None,
                               max_records=None, marker=None):
          
          params = {'DBParameterGroupName' : groupname}
          if source:
              params['Source'] = source
          if max_records:
              params['MaxRecords'] = max_records
          if marker:
              params['Marker'] = marker
          pg = self.get_object('DescribeDBParameters', params, ParameterGroup)
          pg.name = groupname
          return pg
docs: Get all parameters associated with a ParameterGroup
  
          :type groupname: str
          :param groupname: The name of the DBParameter group to retrieve.
  
          :type source: str
          :param source: Specifies which parameters to return.
                         If not specified, all parameters will be returned.
                         Valid values are: user|system|engine-default
  
          :type max_records: int
          :param max_records: The maximum number of records to be returned.
                              If more results are available, a MoreToken will
                              be returned in the response that can be used to
                              retrieve additional records.  Default is 100.
  
          :type marker: str
          :param marker: The marker provided by a previous request.
  
          :rtype: :class:`boto.ec2.parametergroup.ParameterGroup`
          :return: The ParameterGroup