docs: def recreate_parent_dependencies(apps, schema_editor):
      """Create empty dependency relation if parent has been deleted."""
      Data = apps.get_model('flow', 'Data')
      DataDependency = apps.get_model('flow', 'DataDependency')
  
      def process_dependency(data, parent):
          if not Data.objects.filter(pk=parent).exists():
              DataDependency.objects.create(
                  child=data, parent=None, kind='io'
              )
  
      for data in Data.objects.all():
          for field_schema, fields in iterate_fields(data.input, data.process.input_schema):
              name = field_schema['name']
              value = fields[name]
  
              if field_schema.get('type', '').startswith('data:'):
                  process_dependency(data, value)
  
              elif field_schema.get('type', '').startswith('list:data:'):
                  for parent in value:
                      process_dependency(data, parent)