ProductAndQuantity = namedtuple("ProductAndQuantity", ["product", "quantity"])

@register.assignment_tag(takes_context=True)

def available_categories(context):

    ''' Returns all of the available product categories '''

    return rego.Category.objects.all()

@register.assignment_tag(takes_context=True)

def invoices(context):

    ''' Returns all of the invoices that this user has. '''

    return rego.Invoice.objects.filter(cart__user=context.request.user)

@register.assignment_tag(takes_context=True)

def items_pending(context):

    ''' Returns all of the items that this user has in their current cart,

    )

    return all_items

@register.assignment_tag(takes_context=True)

def items_purchased(context):

    ''' Returns all of the items that this user has purchased '''