old_contents: import uuid
  
  from django.contrib.postgres.fields import HStoreField
  from django.db import models
  
  
  class Trainer(models.Model):
  
      """
      People who run training events
      """
      id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
      name = models.CharField(max_length=200)
      msisdn = models.CharField(max_length=20)
      email = models.EmailField(null=True, blank=True)
      extras = HStoreField(null=True, blank=True)
      created_at = models.DateTimeField(auto_now_add=True)
      updated_at = models.DateTimeField(auto_now=True)
  
      def __str__(self):  # __unicode__ on Python 2
          return "Trainer: %s; ID: %s" % (self.name, str(self.id))
  
new_contents: import uuid
  
  from django.contrib.postgres.fields import HStoreField
  from django.db import models
  
  
  class Trainer(models.Model):
  
      """
      People who run training events
      """
      id = models.UUIDField(primary_key=True, default=uuid.uuid4, editable=False)
      name = models.CharField(max_length=200)
      msisdn = models.CharField(max_length=20)
      email = models.EmailField(null=True, blank=True)
      extras = HStoreField(null=True, blank=True)
      created_at = models.DateTimeField(auto_now_add=True)
      updated_at = models.DateTimeField(auto_now=True)
  
      def __str__(self):  # __unicode__ on Python 2
          return "%s" % self.name
  
subject: update trainer model string response