1、修改chaincodeendorsementpolicy.yaml 

identities:  # list roles to be used in the policy
    user1: {"role": {"name": "member", "mspId": "Org1MSP"}} # role member in org with mspid Org1MSP
    user2: {"role": {"name": "member", "mspId": "Org2MSP"}}
    admin1: {"role": {"name": "admin", "mspId": "Org1MSP"}} # admin role.
    admin2: {"role": {"name": "admin", "mspId": "Org2MSP"}}
policy: # the policy  .. could have been flat but show grouping.
    2-of: # signed by one of these groups  can be <n>-of  where <n> is any digit 2-of, 3-of etc..
      - 1-of:
        - signed-by: "user1" # a reference to one of the identities defined above.
        - signed-by: "admin1"
      - 1-of:
        - signed-by: "user2"
        - signed-by: "admin2"
 

2、policy變為2是指需要兩個組織的背書，So，安裝鏈碼必須在兩個組織的peer上安裝，不能在一個組織的不同peer上安裝（無效）； 

3、invoke執行交易的時候，需要返回多個背書的簽名，因此需要傳送個多個有效的peer；