fix failing doc test
@@ -7,7 +7,7 @@ Collimator Toolbox
MU Density
----------
-.. automodule:: pymedphys.mudensity.level1.mudensitycore
+.. automodule:: pymedphys.mudensity._level1.mudensitycore
:no-members:
.. plot:: pyplots/mudensity.py
