def all_gateways_count(bpmn_graph):
return sum([<EOL>count for name, count in get_gateway_counts(bpmn_graph).items()<EOL>])<EOL>
Returns the total count of all gateway elements
in the BPMNDiagramGraph instance.

:param bpmn_graph: an instance of BpmnDiagramGraph representing BPMN model.
:return: total count of the gateway elements in the BPMNDiagramGraph instance