code: func (iamRes *IAMBuilder) ForFederatedPrincipals(principals ...string) *IAMPrincipalBuilder {
  	stringablePrincipals := make([]gocf.Stringable, len(principals))
  	for index, eachPrincipal := range principals {
  		stringablePrincipals[index] = gocf.String(eachPrincipal)
  	}
  
  	return &IAMPrincipalBuilder{
  		builder: iamRes,
  		principal: &gocf.IAMPrincipal{
  			Federated: gocf.StringList(stringablePrincipals...),
  		},
  	}
  }
docs: // ForFederatedPrincipals returns the IAMPrincipalBuilder instance
  // which can be finalized into an IAMRolePrivilege