chainer.functions.pad_sequenceのサンプル
import chainer.functions as F
import chainer
import numpy as np
a=chainer.Variable(np.array([[1],[2],[3]],dtype=np.float32))
b=chainer.Variable(np.array([[11],[12]],dtype=np.float32))
c=chainer.Variable(np.array([[21]],dtype=np.float32))
tpl=(a,b,c)
F.pad_sequence(tpl)
variable([[[ 1.], [ 2.], [ 3.]], [[11.], [12.], [ 0.]], [[21.], [ 0.], [ 0.]]])