code: def get_nodes_id_list_by_type(self, node_type):
          
          tmp_nodes = self.diagram_graph.nodes(data=True)
          id_list = []
          for node in tmp_nodes:
              if node[1][consts.Consts.type] == node_type:
                  id_list.append(node[0])
          return id_list
docs: Get a list of node's id by requested type.
          Returns a list of ids
  
          :param node_type: string with valid BPMN XML tag name (e.g. 'task', 'sequenceFlow').