expo map marker

map.js

import React from 'react';
import { MapView } from 'expo';

export default class App extends React.Component {
  render() {
    return (
      <MapView
        style={{ flex: 1 }}
        initialRegion={{
          latitude: 37.78825,
          longitude: -122.4324,
          latitudeDelta: 0.0922,
          longitudeDelta: 0.0421,
        }}
      >
      <MapView.Marker
      coordinate={{latitude: 37.73538,
          longitude: -122.4324,}}
      title={"marker.title"}
      description={"desss"}
    />
      </MapView>
    );
  }
}