code: func (f *Form) AddInputField(label, value string, fieldWidth int, accept func(textToCheck string, lastChar rune) bool, changed func(text string)) *Form {
  	f.items = append(f.items, NewInputField().
  		SetLabel(label).
  		SetText(value).
  		SetFieldWidth(fieldWidth).
  		SetAcceptanceFunc(accept).
  		SetChangedFunc(changed))
  	return f
  }
docs: // AddInputField adds an input field to the form. It has a label, an optional
  // initial value, a field width (a value of 0 extends it as far as possible),
  // an optional accept function to validate the item's value (set to nil to
  // accept any text), and an (optional) callback function which is invoked when
  // the input field's text has changed.