code: func (b *BigIP) CreateInternalDataGroup(name string, datatype string) error {
  	config := &DataGroup{
  		Name: name,
  		Type: datatype,
  	}
  
  	return b.post(config, uriLtm, uriDatagroup, uriInternal)
  }
docs: // Create an internal data group; dataype must bee one of "ip", "string", or "integer"