code: def get_main_axis(self):
      # if we don't yet have main axis, create one
      if not self._ax_main:
          # by default assign one subplot to whole graph
          self._ax_main = self.figure.add_subplot(
              111, projection=None if not self.is_3d else "3d"
          )
          self._ax_main.grid(self.is_show_grid())
          # change the color of the top and right spines to opaque gray
          self._ax_main.spines["right"].set_color((0.8, 0.8, 0.8))
          self._ax_main.spines["top"].set_color((0.8, 0.8, 0.8))
          if self.title is not None:
              title = self._ax_main.set_title(self.title)
              title.set_weight("bold")
      return self._ax_main
  
file_path: tensorwatch/tensorwatch/mpl/base_mpl_plot.py
imports: from ..vis_base import VisBase
  import sys, logging
  from abc import abstractmethod
  from ..None import utils
label_desc: Use image node_id 3 for calling the BaseMplPlot obj's underlying member method code with example usage: obj.get_main_axis() and returns: self