trainmode!

			trainmode!(m, mode = true)

Set a layer of model's train mode (see below). Symmetric to testmode! (i.e. trainmode!(m, mode) == testmode!(m, !mode)).

Note: if you manually set a model into train mode, you need to manually place it into test mode during testing phase.

Possible values include:

• true for training

• false for testing

• :auto or nothing for Flux to detect the mode automatically