'Sets this objects\'s ACL using a predefined (canned) value.
:type acl_str: string
:param acl_str: A canned ACL string. See
:data:`~.gs.acl.CannedACLStrings`.
:type headers: dict
:param headers: Additional headers to set during the request.
:type generation: int
:param generation: If specified, sets the ACL for a specific generation
of a versioned object. If not specified, the current version is
modified.
:type if_generation: int
:param if_generation: (optional) If set to a generation number, the acl
will only be updated if its current generation number is this value.
:type if_metageneration: int
:param if_metageneration: (optional) If set to a metageneration number,
the acl will only be updated if its current metageneration number is
this value.'

def set_canned_acl(self, acl_str, headers=None, generation=None, if_generation=None, if_metageneration=None):

    if (self.bucket is not None):
        return self.bucket.set_canned_acl(acl_str, self.name, headers=headers, generation=generation, if_generation=if_generation, if_metageneration=if_metageneration)
