Exception Thrown: java.lang.UnsupportedOperationException: PlaceholderMap does not support the .getKeys() method
java.lang.UnsupportedOperationException: PlaceholderMap does not support the .getKeys() method
	at PlaceholderMap.getKeys(PlaceholderMap.java:66)
	at BaseGraph.getAllNodes(BaseGraph.java:106)
	at Backend.loadGraphData(Backend.java:37)
	at WebApp.createWorkingFrontend(WebApp.java:116)
	at WebApp.handleSingleResponse(WebApp.java:173)
	at WebApp.main(WebApp.java:47)