GainPlugin not passing down arguments to GainImputation

[vsimkus]

Hi, thanks for the package.

There's a minor bug in GainPlugin class, in that it doesn't pass down the arguments to GainImputation:

https://github.com/vanderschaarlab/hyperimpute/blob/main/src/hyperimpute/plugins/imputers/plugin_gain.py#L332-L349

To reproduce:

from hyperimpute.plugins.imputers import Imputers

n_epochs=256

gain = Imputers().get('gain', n_epochs=n_epochs)

assert gain._model.n_epochs == n_epochs, 'Argument not passed down'

Also, perhaps the name of the argument "n_epochs" in GAIN should be changed, as it is really the number of gradient steps/iterations, and not passes over the entire dataset (e.g. an epoch).

Hope this helps.