Created by: jacquesqiao

Background

Some Operator needs variable length input, but the current op_proto does not support this feature. So we need to add this.

Discuss

• Add an attr such as "is_sequence_input" into op_proto to tell python to set input as List. the interface of python should be:

fc(input=[x1, x2], y=[y1, y2], ...)

• python will put all the list into one list of input, and set the index into op_desc as attr.