public boolean getAllowFreeFormInput() {
        return mAllowFreeFormTextInput;
    }
Get whether or not users can provide an arbitrary value for
input. If you set this to {@code false}, users must select one of the
choices in {@link #getChoices}. An {@link IllegalArgumentException} is thrown
if you set this to false and {@link #getChoices} returns {@code null} or empty.
android/android_framework/base/src/main/java/github/tornaco/android/thanos/core/compat/RemoteInput.java