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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def list_unique(cls):
		'''Return all unique namespaces

		:returns: a list of all predicates 
		:rtype: list of ckan.model.semantictag.Predicate objects

		'''
		query = meta.Session.query(Predicate).distinct(Predicate.namespace)
		return query.all()