docs: def get_signed_url(self, params):
          '''Returns a Premier account signed url.'''
          params['client'] = self.client_id
          url_params = {'protocol': self.protocol, 'domain': self.domain,
                        'service': self.service, 'params': urlencode(params)}
                        
          secret = base64.urlsafe_b64decode(self.secret_key)
          url_params['url_part'] = (
              '/maps/api/%(service)s/json?%(params)s' % url_params)
          signature = hmac.new(secret, url_params['url_part'], hashlib.sha1)
          url_params['signature'] = base64.urlsafe_b64encode(signature.digest())
  
          return ('%(protocol)s://%(domain)s%(url_part)s'
                  '&signature=%(signature)s' % url_params)