def list_event_handlers(handler_id:nil, target:nil, imsi:nil)
      if handler_id
        [@api.get(path: "/event_handlers/#{handler_id}")]
      elsif imsi
        @api.get(path: "/event_handlers/subscribers/#{imsi}")
      elsif target # target is one of imsi/operator/tag
        @api.get(path: '/event_handlers', params: { target: target })
      else
        @api.get(path: "/event_handlers")
      end
    end
def list_event_handlers(handler_id:nil, target:nil, imsi:nil)
      if handler_id
        [@api.get(path: "/event_handlers/#{handler_id}")]
      elsif imsi
        @api.get(path: "/event_handlers/subscribers/#{imsi}")
      elsif target # target is one of imsi/operator/tag
        @api.get(path: '/event_handlers', params: { target: target })
      else
        @api.get(path: "/event_handlers")
      end
    end
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