docs: static SignaturePolicyEnvelope signedByFabricEntity(String mspId, MSPRoleType role) {
          // specify the principal: it's a member of the msp we just found
          MSPPrincipal principal = MSPPrincipal
                  .newBuilder()
                  .setPrincipalClassification(Classification.ROLE)
                  .setPrincipal(MSPRole
                          .newBuilder()
                          .setMspIdentifier(mspId)
                          .setRole(role)
                          .build().toByteString())
                  .build();
  
          // create the policy: it requires exactly 1 signature from the first (and only) principal
          return SignaturePolicyEnvelope
                  .newBuilder()
                  .setVersion(0)
                  .setRule(nOutOf(1, Arrays.asList(signedBy(0))))
                  .addIdentities(principal)
                  .build();
  
      }