class_docstr: Provides methods for retrieving data on different cryptocurrencies from
  https://www.cryptodatadownload.com/cdd/.
  
  Attributes
  ----------
  url : str
      The url for collecting data from CryptoDataDownload.
  
  Methods
  -------
  fetch(exchange_name,base_symbol,quote_symbol,timeframe,include_all_volumes=False)
      Fetches data for different exchanges and cryptocurrency pairs.
code: def __init__(self) -> None:
      self.url = "https://www.cryptodatadownload.com/cdd/"
  
imports: import ssl
  import pandas
label_desc: Use image node_id 1 to create a new CryptoDataDownload object  with example: obj = CryptoDataDownload()