docstr: Test FFN block.
docstr_tok: ["Test","FFN","block","."]
code: def test_ffn(self):
      """
      Test FFN block.
      """
      x = torch.randn(1, 3, 1, 3)
      layer1 = FFNBlock(in_channels=3)
      layer2 = FFNBlock(
          in_channels=3, hidden_channels=2, out_channels=2
      )
      y1 = layer1(x)
      y2 = layer2(x)
      # print(y1.shape, y2.shape)
      self.assertTrue(y1.shape == torch.Size([1, 3, 1, 3]))
      self.assertTrue(y2.shape == torch.Size([1, 2, 1, 3]))
  
imports: import torch
  import unittest
  from towhee.models.layers.ffn import FFNBlock
label_desc: Use image node_id 1 for calling the ConvBNActivationTest obj's underlying member method code with example usage: obj.test_ffn() without return types