Convolution.

def _conv(self, name, x, filter_size, in_filters, out_filters, strides):
    """Convolution."""
    if self.init_layers:
      conv = Conv2DnGPU(out_filters,
                        (filter_size, filter_size),
                        strides[1:3], 'SAME', w_name='DW')
      conv.name = name
      self.layers += [conv]
    else:
      conv = self.layers[self.layer_idx]
      self.layer_idx += 1
    conv.device_name = self.device_name
    conv.set_training(self.training)
    return conv.fprop(x)