Log out button in drawer navigation - React native

Im trying to implement a button Log out into the drawer navigation. I have the function signOut that I want to call when I clcik on the button Log out from the drawer navigation :

App.js :

 const AppHomeTeacherDrawerNavigator = createDrawerNavigator({
  Home: {
    screen: Home,
    navigationOptions: {
      title: "Menu",
      drawerIcon: () => <Icon name="home" size={25} />,
    },
  },

  SettingsScreen: {
    screen: SettingsScreen,
    navigationOptions: {
      title: "Log out",
      drawerIcon: () => <Icon name="settings" size={25} />,
    },
  },
}); 

SettingsScreen.js :

export default class SettingsScreen extends React.Component {
  signOut = async () => {
    try {
      await firebase.auth().signOut();
      this.props.navigation.navigate("WelcomeScreen");
    } catch (error) {
      Alert.alert("", "");
    }
  };


  render() {
    return (
      <View>
       <CustomValidationButton onPress={this.signOut}>
              <Text>Log out</Text>
            </CustomValidationButton>
      </View>  
    );
  }
}