code: def get_block_currencies():
      
      return ['btc', 'ltc', 'ppc', 'dash', 'doge', 'ric']
      currencies = []
      for currency, data in crypto_data.items():
          if type(data) is list:
              continue
          block_services = data.get('services', {}).get('get_block', [])
          if len(block_services) > 0 and not all([x.get_block.by_latest for x in block_services]):
  
              currencies.append(currency)
  
      return currencies
docs: Returns a list of all curencies (by code) that have a service defined that
      implements `get_block`.