'Set multiple keys\' values at once, regardless of previous contents.
Args:
mapping: Dictionary of keys to values.
time: Optional expiration time, either relative number of seconds
from current time (up to 1 month), or an absolute Unix epoch time.
By default, items never expire, though items may be evicted due to
memory pressure.  Float values will be rounded up to the nearest
whole second.
key_prefix: Prefix for to prepend to all keys.
min_compress_len: Unimplemented compatibility option.
namespace: a string specifying an optional namespace to use in
the request.
Returns:
A list of keys whose values were NOT set.  On total success,
this list should be empty.'

def set_multi(self, mapping, time=0, key_prefix='', min_compress_len=0, namespace=None):

    return self._set_multi_with_policy(MemcacheSetRequest.SET, mapping, time=time, key_prefix=key_prefix, namespace=namespace)
