old_contents: import time
  import hmac
  import hashlib
  import datetime
  import pytz
  
  def nounce():
      '''
      return utc unix time in second
  
      TODO: 
      - return utc unix time in micro second
      '''
      return str(int(time.mktime(datetime.datetime.now(pytz.utc).timetuple())))
  
  def make_header(url,
                  access_key=None,
                  secret_key=None):
      ''' create request header function
      :param url: URL for the new :class:`Request` object.
      '''
      nonce = nounce()
      url    = url
      message = nonce + url
      signature = hmac.new(secret_key.encode('utf-8'), message.encode('utf-8'), hashlib.sha256).hexdigest()
      headers = {
         'ACCESS-KEY'      : access_key,
         'ACCESS-NONCE'    : nonce,
         'ACCESS-SIGNATURE': signature
      }
      return headers
  
  
new_contents: import time
  import hmac
  import hashlib
  import datetime
  import pytz
  
  def nounce():
      '''
      return utc unix time in second
  
      TODO: 
      - return utc unix time in micro second
      '''
      return str(int(time.time() * 1000000000))
  
  def make_header(url,
                  access_key=None,
                  secret_key=None):
      ''' create request header function
      :param url: URL for the new :class:`Request` object.
      '''
      nonce = nounce()
      url    = url
      message = nonce + url
      signature = hmac.new(secret_key.encode('utf-8'), message.encode('utf-8'), hashlib.sha256).hexdigest()
      headers = {
         'ACCESS-KEY'      : access_key,
         'ACCESS-NONCE'    : nonce,
         'ACCESS-SIGNATURE': signature
      }
      return headers
  
  
subject: modify nounce: sec to micro sec * 1000000000