views.py

...  # Other imports
import requests
import get_client_ip from './utils.py'  # See next snippet

secret_key = 'YOUR_SECRET_SITE_KEY'  # Preferably from settings.py

class Submission(APIView):
  ...
  
  def post(self, request, *args, **kwargs):
    r = requests.post(
      'https://www.google.com/recaptcha/api/siteverify',
      data={
        'secret': secret_key,
        'response': request.data['g-recaptcha-response'],
        'remoteip': get_client_ip(self.request),  # Optional
      }
    )

    if r.json()['success']:
      # Successfuly validated
      # Handle the submission, with confidence!
      return self.create(request, *args, **kwargs)

    # Error while verifying the captcha 
    return Response(data={'error': 'ReCAPTCHA not verified.'}, status=status.HTTP_406_NOT_ACCEPTABLE)