'Add an attribute to the element
In case you need to add an attribute the library doesn\'t know about
then you must provide the full qualified name
It will not check that the attribute is legal according to the schema.
Must overwrite, If attribute already exists.'

def setAttrNS(self, namespace, localpart, value):

    allowed_attrs = self.allowed_attributes()
    prefix = self.get_nsprefix(namespace)
    c = AttrConverters()
    self.attributes[(namespace, localpart)] = c.convert((namespace, localpart), value, self)
