#!/usr/bin/env python3
import megengine as mge
import megengine.module as nn
import megengine.functional as F

def conv3x3(in_chn, out_chn, bias=True):
    layer = nn.Conv2d(in_chn, out_chn, kernel_size=3, stride=1, padding=1, bias=bias)
    return layer


def conv_down(in_chn, out_chn, bias=False):
    layer = 
nn.Conv2d(in_chn, out_chn, kernel_size=4, stride=2, padding=1, bias=bias)