text: from django.db.models.signals import pre_migrate, post_migrate
  
  from security.backends.app import SecurityBackend
  
  from . import db_helpers
  
  
  def start_migration(sender, **kwargs):
      db_helpers.is_running_migration = True
  
  
  def end_migration(sender, **kwargs):
      db_helpers.is_running_migration = False
  
  
  class SecuritySQLBackend(SecurityBackend):
  
      name = 'security.backends.sql'
      label = 'security_backends_sql'
      backend_name = 'sql'
      writer = 'security.backends.sql.writer.SQLBackendWriter'
      reader = 'security.backends.sql.reader.SQLBackendReader'
  
      def ready(self):
          super().ready()
          pre_migrate.connect(start_migration, sender=self)
          post_migrate.connect(end_migration, sender=self)
  