code: def import_data_object_to_graph(diagram_graph, process_id, process_attributes, data_object_element):
          
          BpmnDiagramGraphImport.import_flow_node_to_graph(diagram_graph, process_id, process_attributes,
                                                           data_object_element)
          data_object_id = data_object_element.getAttribute(consts.Consts.id)
          diagram_graph.node[data_object_id][consts.Consts.is_collection] = \
              data_object_element.getAttribute(consts.Consts.is_collection) \
                  if data_object_element.hasAttribute(consts.Consts.is_collection) else "false"
docs: Adds to graph the new element that represents BPMN data object.
          Data object inherits attributes from FlowNode. In addition, an attribute 'isCollection' is added to the node.
  
          :param diagram_graph: NetworkX graph representing a BPMN process diagram,
          :param process_id: string object, representing an ID of process element,
          :param process_attributes: dictionary that holds attribute values of 'process' element, which is parent of
              imported flow node,
          :param data_object_element: object representing a BPMN XML 'dataObject' element.