code: func expandSliceOfCustomizationAdapterMapping(d *schema.ResourceData) []types.CustomizationAdapterMapping {
  	s := d.Get(cKeyPrefix + "." + "network_interface").([]interface{})
  	if len(s) < 1 {
  		return nil
  	}
  	result := make([]types.CustomizationAdapterMapping, len(s))
  	var v4gwFound, v6gwFound bool
  	for i := range s {
  		var adapter types.CustomizationIPSettings
  		adapter, v4gwFound, v6gwFound = expandCustomizationIPSettings(d, i, !v4gwFound, !v6gwFound)
  		obj := types.CustomizationAdapterMapping{
  			Adapter: adapter,
  		}
  		result[i] = obj
  	}
  	return result
  }
docs: // expandSliceOfCustomizationAdapterMapping reads certain ResourceData keys and
  // returns a CustomizationAdapterMapping slice.