def register
      response_request = Request.post("transactions/cancels", api_version, params)
      Response.new(response_request, self).serialize
    end
def register
      response_request = Request.post("transactions/cancels", api_version, params)
      Response.new(response_request, self).serialize
    end
Calls the PagSeguro webservice and register the cancellation.
 Returns PagSeguro::TransactionCancellation.