'Open this key for reading
:type headers: dict
:param headers: Headers to pass in the web request
:type query_args: string
:param query_args: Arguments to pass in the query string
(ie, \'torrent\')
:type override_num_retries: int
:param override_num_retries: If not None will override configured
num_retries parameter for underlying GET.
:type response_headers: dict
:param response_headers: A dictionary containing HTTP
headers/values that will override any headers associated
with the stored object in the response.  See
http://goo.gl/EWOPb for details.'

def open_read(self, headers=None, query_args='', override_num_retries=None, response_headers=None):

    if self.generation:
        if query_args:
            query_args += '&'
        query_args += ('generation=%s' % self.generation)
    super(Key, self).open_read(headers=headers, query_args=query_args, override_num_retries=override_num_retries, response_headers=response_headers)
