Filter product by tag [TaggedProduct classmethod]

filter_products_by_tag.py

class TaggedProducts(GenericTaggedItemBase):
	
	[...]
	
	# filter products by tags
	@classmethod
	def filter(cls, *tags):
		products = Products.objects.all()
		for tag in tags:
			if tag not in (t.slug for t in ProductTags.objects.all()): # not good for speed
				return "%s tag does not exists, please try with valid tags" % (tag)		
			products = products.filter(tags__slug__in=[tag])
		return products if len(products) > 0 else "No products tagged with %s" % (", ".join(tags))