Traffic Lights, Signs and Controls: Did Not See Stop Sign Because View Obstructed by School Bus

My question involves a traffic ticket from the state of: California for failure to stop, VC 22450a, at a posted stop sign. View of stop sign was obstructed by three school buses. I have photographs showing view of obstruction. There was a crosswalk and the word stop painted on the street which I did not see. What method do I use to fight this citation.

Traffic Lights, Signs and Controls: Did Not See Stop Sign Because View Obstructed by School Bus