def source_key(resp):
 return float((resp.getheader('x-put-timestamp') or resp.getheader('x-timestamp') or 0))

def source_key ( resp ) : return float ( ( resp . getheader ( 'x-put-timestamp' ) or resp . getheader ( 'x-timestamp' ) or 0 ) )
provide the timestamp of the swift http response as a floating point value .