code: func WithProviderUser(username string, org string) ProviderOption {
  	return func(opts *ProviderUsersOptions) error {
  
  		si := mspmocks.NewMockSigningIdentity(username, org)
  		opts.identity = si
  
  		userMap := make(map[string]msp.SigningIdentity)
  		userMap[username] = si
  		orgMap := make(map[string]map[string]msp.SigningIdentity)
  		orgMap[org] = userMap
  		opts.users = orgMap
  
  		return nil
  	}
  }
docs: // WithProviderUser option