feature(Util): Create plotting for `y` and `predictions`.

[szemyd]

  import pandas as pd
  def plot_y_and_predictions(y: pd.Series, preds: pd.DataFrame):
      df = pd.DataFrame({"y": y, "predictions": preds.squeeze()})
      df.plot(secondary_y=['predictions'], mark_right=False, figsize = (20,5), grid=True, alpha=0.7)