code: def base_url(self, base_url=None):
          
          if base_url:
              # POSTs need to be over HTTPS (e.g., Import API reverts to a GET)
              if urlparse(base_url).scheme != 'https':
                  raise ValueError(
  		    '`base_url`s need to be over `https`. Update your '
                      '`base_url`.'
  		)
              self._base_url = base_url
          else:
              return self._base_url
docs: Return or set `base_url`.
  
          Args:
              base_url (str, optional): If set, updates the `base_url`. Otherwise
                  returns current `base_url`.
  
          Note:
              This does not update the `username` attribute. Separately update
              the username with ``Credentials.username`` or update `base_url` and
              `username` at the same time with ``Credentials.set``.
  
          Example:
  
              .. code::
  
                  >>> from cartoframes import Credentials
                  # load credentials saved in previous session
                  >>> creds = Credentials()
                  # returns current base_url
                  >>> creds.base_url()
                  'https://eschbacher.carto.com/'
                  # updates base_url with new value
                  >>> creds.base_url('new_base_url')