code: def _addBase(self, position, xlabel=None, ylabel=None):
      
      ax = self._fig.add_subplot(position)
      ax.set_xlabel(xlabel)
      ax.set_ylabel(ylabel)
      return ax
docs: Adds a subplot to the plot's figure at specified position.
  
      @param position A 3-digit number. The first two digits define a 2D grid
              where subplots may be added. The final digit specifies the nth grid
              location for the added subplot
      @param xlabel text to be displayed on the x-axis
      @param ylabel text to be displayed on the y-axis
      @returns (matplotlib.Axes) Axes instance