code: def from_yaml(self, filename, encoding='utf-8', silent=False):
          
          if not yaml:
              raise AttributeError(
                  'You need to install PyYAML before using this method!')
  
          self.from_file(yaml.load, filename, encoding, silent)
docs: Updates recursively the value in the the config from a YAML file.
  
          The method requires the PyYAML to be installed.
  
          :param filename: (str) a filename of the YAML file
          :param encoding: (str) an encoding of the filename
          :param silent: (bool) fails silently if something wrong with yaml file
  
          .. versionadded:: 0.3.0