code: def prepare(self, params):
          
          jsonparams = json.dumps(params)
          payload = base64.b64encode(jsonparams.encode())
          signature = hmac.new(self.secret_key.encode(), payload,
                               hashlib.sha384).hexdigest()
  
          return {'X-GEMINI-APIKEY': self.api_key,
                  'X-GEMINI-PAYLOAD': payload,
                  'X-GEMINI-SIGNATURE': signature}
docs: Prepare, return the required HTTP headers.
  
          Base 64 encode the parameters, sign it with the secret key,
          create the HTTP headers, return the whole payload.
  
          Arguments:
          params -- a dictionary of parameters