code: def buyLimit(self, limitPrice, quantity):
      url = "https://www.bitstamp.net/api/buy/"
  
      # Rounding price to avoid 'Ensure that there are no more than 2 decimal places'
      # error.
      price = round(limitPrice, 2)
      # Rounding amount to avoid 'Ensure that there are no more than 8 decimal places'
      # error.
      amount = round(quantity, 8)
  
      params = {"price": price, "amount": amount}
      jsonResponse = self._post(url, params)
      return Order(jsonResponse)
  
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 7 for calling the HTTPClient obj's underlying member method code with example usage: obj.buyLimit(limitPrice, quantity) and returns: Order