code: def configure_from_environment(self, whitelist_keys=False, whitelist=None):
          
          self._configure_from_mapping(os.environ, whitelist_keys=whitelist_keys,
                                       whitelist=whitelist)
  
          return self
docs: Configure from the entire set of available environment variables.
  
          This is really a shorthand for grabbing ``os.environ`` and passing to
          :meth:`_configure_from_mapping`.
  
          As always, only uppercase keys are loaded.
  
          Keyword Args:
              whitelist_keys (bool):
                  Should we whitelist the keys by only pulling those that are
                  already present in the config? Useful for avoiding adding
                  things like ``LESSPIPE`` to your app config. If no whitelist is
                  provided, we use the current config keys as our whitelist.
              whitelist (list[str]):
                  An explicit list of keys that should be allowed. If provided
                  and ``whitelist_keys`` is true, we will use that as our
                  whitelist instead of pre-existing app config keys.
  
          Returns:
              fleaker.base.BaseApplication:
                  Returns itself.