Google Maps computeRoutes Polyline Decode using Flutter/Dart

Question

I'm attempting to extract routes from the computeRoutes method from the Google Maps API (https://developers.google.com/maps/documentation/routes/reference/rest/v2/TopLevel/computeRoutes). I'm able to get the correct response each time, which I verify here (https://developers.google.com/maps/documentation/routes/polylinedecoder), but when I use json.encode and then json.decode(response.body), the encodedPolyline comes back altered because certain escape character sequences are adjusted (two backslashes in my case \). Why is this the case? Should I be using a different method? The original response.body works just fine when I log it into my console, so I'm not sure what the issues is: //server.js

app.post('/api/computeRoutes', async (req, res) => {
      const { origin, destination, travelMode } = req.body;
      const apiKey = process.env.GOOGLE_MAPS_API_KEY;
    
      const [originLat, originLng] = origin.split(',').map(Number);
      const [destinationLat, destinationLng] = destination.split(',').map(Number);
    
      const url = `https://routes.googleapis.com/directions/v2:computeRoutes?key=${apiKey}`;
    
      const data = {
        origin: {
          location: {
            latLng: {
              latitude: originLat, 
              longitude: originLng
            } 
          }
        },
        destination: {
          location: { 
            latLng: { 
              latitude: destinationLat, 
              longitude: destinationLng 
            } 
          }
        },
        travelMode: "DRIVE"
        // travelMode: travelMode.toUpperCase() || 'DRIVING'
      };
    
      const headers = {
        'Content-Type': 'application/json',
        'X-Goog-FieldMask': 'routes.duration,routes.distanceMeters,routes.polyline.encodedPolyline'
      };
      
      try {
        const response = await axios.post(url, data, { headers });
        console.log(`Server.js Response Data: ${JSON.stringify(response.data)}`);
        res.json(response.data);
      } catch (error) {
        console.error('Error in computeRoutes:', error);
        res.status(500).send('Error occurred while fetching routes');
      }
    });

//map_service.dart

  Future<dynamic> getDirections(String origin, String destination, {String travelMode = 'DRIVING'}) async {
    final url = '$_baseUrl/api/computeRoutes';

    final response = await http.post(
      Uri.parse(url),
      headers: {"Content-Type": "application/json"},
      body: json.encode({
        'origin': origin,
        'destination': destination,
        'travelMode': travelMode,
      }),
    );

    if (response.statusCode == 200) {
      String responseBody = response.body;
      return json.decode(response.body); // Adjust according to your server's response format
    } else {
      throw Exception('Failed to get directions: ${response.body}');
    }
  }