What type is assigned to props.navigation.navigate in Typescript? (React Native)

I'm trying to pass as props a function which will return props.navigation.navigate and change the screen:

    handleSubmit = (formState: AddContactFormState) => {        this.props.navigation.navigate('ContactList', { newContact: formState })    }    render() {        return <AddContactForm onSubmit={this.handleSubmit} />    }

In my types.tsx file:

export type AddContactFormProps = {    fn: (formState: AddContactFormState) => /* ??? */}

Any help would be greatly appreciated as I was unable to find any docs explaining all the types in React Navigation. Thanks.