code: def plot_acquisition(self,filename=None):
          
          if self.model.model is None:
              from copy import deepcopy
              model_to_plot = deepcopy(self.model)
              if self.normalize_Y:
                  Y = normalize(self.Y, self.normalization_type)
              else:
                  Y = self.Y
              model_to_plot.updateModel(self.X, Y, self.X, Y)
          else:
              model_to_plot = self.model
  
          return plot_acquisition(self.acquisition.space.get_bounds(),
                                  model_to_plot.model.X.shape[1],
                                  model_to_plot.model,
                                  model_to_plot.model.X,
                                  model_to_plot.model.Y,
                                  self.acquisition.acquisition_function,
                                  self.suggest_next_locations(),
                                  filename)
docs: Plots the model and the acquisition function.
              if self.input_dim = 1: Plots data, mean and variance in one plot and the acquisition function in another plot
              if self.input_dim = 2: as before but it separates the mean and variance of the model in two different plots
          :param filename: name of the file where the plot is saved