These filters allow django template use of elements beginning with an underscore character.
The sole purpose of these filters are to allow operations with template elements that naturally start with the underscore ('_') character.
Usage: field_
Example:
{{ form|field_:'_field_name' }}
Usage: attr_
Example:
{{ my_tag|attr_:'_attr_name' }}
Usage: dict_
Example:
{{ my_dict|dict_:'_key_name' }}
http://stackoverflow.com/questions/6676045/accessing-couchdbs-uuid-in-django-templates http://stackoverflow.com/questions/13693888/accessing-dict-elements-with-leading-underscores-in-django-templates