RadioButton.with_mnemonic
Description:
[ CCode ( has_construct_function = false ,  type = "GtkWidget*" ) ]
public RadioButton.with_mnemonic (SList<RadioButton>? group, string label)
  public RadioButton.with_mnemonic (SList<RadioButton>? group, string label)
Creates a new RadioButton containing a label, adding it to the same group as 
        group.
 The label will be created using Label.with_mnemonic, so 
      underscores in label indicate the mnemonic for the button.
Parameters:
| group | the radio button group, or null | 
| label | the text of the button, with an underscore in front of the mnemonic character | 
Returns:
| a new RadioButton |