code: def DoubleConvUnit(i1, i2):
      double_conv_layer = nn.Sequential(
          ConvLayer(i1, kernel=3), ConvLayer(i2, kernel=3)
      )
      return double_conv_layer
  
imports: import nnabla
  import nnabla.parametric_functions
  import nnabla.functions
  import numpy
  import pytest
  from helper import create_temp_with_dir
  from nnabla.testing import assert_allclose
label_desc: Use image node_id 1 for calling a global function with example usage: DoubleConvUnit(i1, i2) and returns: double_conv_layer