docs: def get_parameter_dd(self, parameter):
          """
          This method returns parameters as nested dicts in case of decision
          diagram parameter.
          """
          dag = defaultdict(list)
          dag_elem = parameter.find('DAG')
          node = dag_elem.find('Node')
          root = node.get('var')
  
          def get_param(node):
              edges = defaultdict(list)
              for edge in node.findall('Edge'):
                  if edge.find('Terminal') is not None:
                      edges[edge.get('val')] = edge.find('Terminal').text
                  elif edge.find('Node') is not None:
                      node_cpd = defaultdict(list)
                      node_cpd[edge.find('Node').get('var')] = \
                          get_param(edge.find('Node'))
                      edges[edge.get('val')] = node_cpd
                  elif edge.find('SubDAG') is not None:
                      subdag_attribute = defaultdict(list)
                      subdag_attribute['type'] = edge.find('SubDAG').get('type')
                      if subdag_attribute['type'] == 'template':
                          subdag_attribute['idref'] = \
                              edge.find('SubDAG').get('idref')
                      if edge.find('SubDAG').get('var'):
                          subdag_attribute['var'] = \
                              edge.find('SubDAG').get('var')
                      if edge.find('SubDAG').get('val'):
                          subdag_attribute['val'] = \
                              edge.find('SubDAG').get('val')
                      edges[edge.get('val')] = subdag_attribute
              return edges
  
          if parameter.find('SubDAGTemplate') is not None:
              SubDAGTemplate = parameter.find('SubDAGTemplate')
              subdag_root = SubDAGTemplate.find('Node')
              subdag_node = subdag_root.get('var')
              subdag_dict = defaultdict(list)
              subdag_dict[subdag_node] = get_param(subdag_root)
              dag['SubDAGTemplate'] = subdag_dict
              dag['id'] = SubDAGTemplate.get('id')
          dag[root] = get_param(node)
          return dag