code: func SigningAccounts(concretePrivateAccounts []*PrivateAccount) []AddressableSigner {
  	signingAccounts := make([]AddressableSigner, len(concretePrivateAccounts))
  	for i, cpa := range concretePrivateAccounts {
  		signingAccounts[i] = cpa
  	}
  	return signingAccounts
  }
docs: // Convert slice of ConcretePrivateAccounts to slice of SigningAccounts