text: import {createStackNavigator} from 'react-navigation-stack';
  
  import PomodoroScreen from '../screens/PomodoroScreen';
  import Header from '../components/header';
  import React from 'react';
  //if we use stack navigator, it will also include a header
  
  const screens = {
  
      //what screen to show
      //the first screen object will be the first screen that the app will show (order matters!)
      Pomodoro :{
          screen: PomodoroScreen,
          navigationOptions: ({navigation}) => {
              return {
                  headerTitle:  () => <Header navigation={navigation} title='Pomodoro Timer'/>
              }
          }
      }
  }
  
  const todoListScreenStack = createStackNavigator(screens, {
      defaultNavigationOptions:{
          headerTintColor: "#444",
          headerStyle: {backgroundColor: '#000014', height: 70}
      }
  })
  
  export default todoListScreenStack;