text: """This module corresponds to functionality documented at 
  https://blockchain.info/api/exchange_rates_api
  """
  
  import json
  from . import util
  
  
  def get_ticker(api_code=None):
      """Call the 'ticker' method and return a dictionary
      of :class:`Currency` objects.
      
      :param str api_code: Blockchain.info API code (optional)
      :return: a dictionary in the format of ccy_symbol(str):currency(:class:`Currency`)
      """
      
      response = util.call_api('ticker' if api_code is None else 'ticker?api_code=' + api_code)
      json_response = json.loads(response)
      ticker = {}
      for key in json_response:
          json_ccy = json_response[key]
          ccy = Currency(json_ccy['last'],
                         json_ccy['buy'],
                         json_ccy['sell'],
                         json_ccy['symbol'],
                         json_ccy['15m'])
          ticker[key] = ccy
      return ticker
  
  
  def to_btc(ccy, value, api_code=None):
      """Call the 'tobtc' method and convert x value in the provided currency to BTC.
      
      :param str ccy: currency code
      :param float value: value to convert
      :param str api_code: Blockchain.info API code
      :return: the value in BTC
      """
      
      res = 'tobtc?currency={0}&value={1}'.format(ccy, value)
      if api_code is not None:
          res += '&api_code=' + api_code
      return float(util.call_api(res))
  
  
  def to_fiat(ccy, value, api_code=None):
      """Call the 'frombtc' method and convert x value in the provided currency to BTC.
  
      :param str ccy: currency code
      :param float value: BTC value to convert
      :param str api_code: Blockchain.info API code
      :return: the value in fiat currency
      """
  
      res = 'frombtc?currency={0}&value={1}'.format(ccy, value*100000000)
      if api_code is not None:
          res += '&api_code=' + api_code
      return float(util.call_api(res))
  
  
  class Currency:
      def __init__(self, last, buy, sell, symbol, p15min):
          self.last = last
          self.buy = buy
          self.sell = sell
          self.symbol = symbol
          self.p15min = p15min
  