title: Get output from Lasagne (python deep neural network framework)
body: <p>I loaded the mnist_conv.py example from official github of Lasagne.</p>
  
  <p>At the and, I would like to predict my own example. I saw that "lasagne.layers.get_output()" should handle numpy arrays from official documentation, but it doesn't work and I cannot figure out how can I do that.</p>
  
  <p>Here's my code:</p>
  
  <pre><code>if __name__ == '__main__':
      output_layer = main() #the output layer from the net
      exampleChar = np.zeros((28,28)) #the example I would predict
      outputValue = lasagne.layers.get_output(output_layer, exampleChar)
      print(outputValue.eval())
  </code></pre>
  
  <p>but it gives me:</p>
  
  <pre><code>TypeError: ConvOp (make_node) requires input be a 4D tensor; received "TensorConstant{(28, 28) of 0.0}" (2 dims)
  </code></pre>
  
  <p>I understand that it expects a 4D tensor, but I don't have any idea how to correct it.</p>
  
  <p>Can you help me? Thanks</p>