Using fi function to quantize weights

I want to use the fi function to change the weights of a deep neural network from type single to type int8 i.e quantizing the weights from 32-bit to 8-bit.

Running this line of code:

net.Layers(2,1).Weights = fi( net.Layers(2,1).Weights, 1, 8 );

throws this error:

Error using nnet.cnn.layer.Convolution2DLayer/set.Weights (line 250)

Expected input to be one of these types:

single, double

Instead its type was embedded.fi.

Please, is there a way to do what I want?