code: func (r Dns_Domain_Registration) AddNameserversToDomain(nameservers []string) (resp bool, err error) {
  	params := []interface{}{
  		nameservers,
  	}
  	err = r.Session.DoRequest("SoftLayer_Dns_Domain_Registration", "addNameserversToDomain", params, &r.Options, &resp)
  	return
  }
docs: // The addNameserversToDomain method adds nameservers to a domain for a domain that already has nameservers assigned to it. This method does not create a nameserver; the nameserver must already exist.