code: def getUserTransactions(self, transactionType=None):
      url = "https://www.bitstamp.net/api/user_transactions/"
      jsonResponse = self._post(url, {})
      if transactionType is not None:
          jsonUserTransactions = filter(
              lambda jsonUserTransaction: jsonUserTransaction["type"]
              == transactionType,
              jsonResponse,
          )
      else:
          jsonUserTransactions = jsonResponse
      return [
          UserTransaction(jsonUserTransaction)
          for jsonUserTransaction in jsonUserTransactions
      ]
  
imports: import time
  import datetime
  import hmac
  import hashlib
  import requests
  import threading
  from pyalgotrade.utils import dt
  from pyalgotrade.bitstamp import common
  import logging
label_desc: Use image node_id 9 for calling the HTTPClient obj's underlying member method code with example usage: obj.getUserTransactions(transactionType) and returns: unknown