code: def _get_signed_url(self, params):
          
          params['client'] = self.client_id
  
          if self.channel:
              params['channel'] = self.channel
  
          path = "?".join((self.api_path, urlencode(params)))
          signature = hmac.new(
              base64.urlsafe_b64decode(self.secret_key),
              path.encode('utf-8'),
              hashlib.sha1
          )
          signature = base64.urlsafe_b64encode(
              signature.digest()
          ).decode('utf-8')
          return '%s://%s%s&signature=%s' % (
              self.scheme, self.domain, path, signature
          )
docs: Returns a Premier account signed url. Docs on signature:
              https://developers.google.com/maps/documentation/business/webservices/auth#digital_signatures