don't cover untestable code
@@ -189,7 +189,7 @@ class PID_downarrow(BaseUniquePID):
_measure = staticmethod(i_downarrow)
-def i_double_downarrow(d, inputs, output, nhops=5):
+def i_double_downarrow(d, inputs, output, nhops=5): # pragma: no cover
"""
This computes unique information as I(input : output \Downarrow other_inputs).
