code: public CompletableFuture<TransactionEvent> sendTransaction(Collection<? extends ProposalResponse> proposalResponses, Collection<Orderer> orderers) {
  
          return sendTransaction(proposalResponses, orderers, client.getUserContext());
      }
docs: Send transaction to one of the specified orderers using the usercontext set on the client..
  
  @param proposalResponses The proposal responses to be sent to the orderer
  @param orderers          The orderers to send the transaction to.
  @return a future allowing access to the result of the transaction invocation once complete.