Fixing a small bug in schema where the number of default arguments doesn't match the number of fields
Fixing a small bug in schema where the number of default arguments doesn't match the number of fields

Summary:
The current version of schema.py has a Metadata class with three fields. The default for it is set to
four Nones. This is just changing that to three Nones so that the number of default values matches the number
of actual fields.

Reviewed By: kennyhorror

Differential Revision: D5250463

fbshipit-source-id: 42e5650d270f5f63662614d8445b4819ed370dec

davinwang/caffe2,Yangqing/caffe2,Yangqing/caffe2,davinwang/caffe2,sf-wind/caffe2,xzturn/caffe2,xzturn/caffe2,xzturn/caffe2,pietern/caffe2,Yangqing/caffe2,davinwang/caffe2,bwasti/caffe2,davinwang/caffe2,bwasti/caffe2,bwasti/caffe2,bwasti/caffe2,sf-wind/caffe2,Yangqing/caffe2,sf-wind/caffe2,pietern/caffe2,Yangqing/caffe2,sf-wind/caffe2,pietern/caffe2,davinwang/caffe2,xzturn/caffe2,bwasti/caffe2,pietern/caffe2,xzturn/caffe2,caffe2/caffe2,sf-wind/caffe2,pietern/caffe2