def __create_reference(self, content_id, name=None, target_id=0,
tags=None, factory=ReferenceValue):
"""Create and add a new reference
"""
if not IReferenceValue.implementedBy(factory):
raise TypeError('Wrong factory %s for reference, '
'it should implement IReferenceValue' % factory)
if tags is None:
tags = []
if name is not None:
tags.append(name)
reference = factory(content_id, target_id, tags=tags)
reference_id = str(uuid.uuid4())
self.references[reference_id] = reference
return reference
