returns a bucket's acl. We include a version_id argument
           to support a polymorphic interface for callers, however, 
           version_id is not relevant for Google Cloud Storage buckets 
           and is therefore ignored here.

def get_acl(self, key_name='', headers=None, version_id=None):
        """returns a bucket's acl. We include a version_id argument
           to support a polymorphic interface for callers, however, 
           version_id is not relevant for Google Cloud Storage buckets 
           and is therefore ignored here.""" 
        return self.get_acl_helper(key_name, headers, STANDARD_ACL)