You must be looking at the other guys code. Mine is this.
from arcrest.security import AGOLTokenSecurityHandler
from arcrest.agol import FeatureService
from arcrest.common.filters import LayerDefinitionFilter
#Get a local replica of the HFS
proxy_port = None
proxy_url = None
agolSH = AGOLTokenSecurityHandler(username=username,password=password)
fs = FeatureService(url=url,securityHandler=agolSH,proxy_port=proxy_port,proxy_url=proxy_url,initialize=True)
result = fs.createReplica(replicaName='Demo', layers='0,1,2,3', keep_replica=False, layerQueries=None, geometryFilter=None, returnAttachments=True,returnAttachmentDatabyURL=False,returnAsFeatureClass=True, out_path=outDir)