code: def save(self, *args, **kwargs):
      if self.mat_plot_id is None:
          self.mat_plot_id = uuid4()
  
      return super(ExperimentMatPlot, self).save(*args, **kwargs)
  
imports: from uuid import uuid4
  from django.db import models
  from modelchimp.models.project import Project
  from modelchimp.models.experiment import Experiment
label_desc: Use image node_id 1 for calling the ExperimentMatPlot obj's underlying member method code with example usage: obj.save() and returns: super