Fixed doctest input that was failing

Author: oesteban

nipype/algorithms/misc.py

@@ -1230,7 +1230,7 @@ class NormalizeProbabilityMapSet(BaseInterface):
     >>> import nipype.algorithms.misc as misc
     >>> normalize = misc.NormalizeProbabilityMapSet()
     >>> normalize.inputs.in_files = [ 'tpm_00.nii.gz', 'tpm_01.nii.gz', 'tpm_02.nii.gz' ]
-    >>> normalize.inputs.in_mask = [ 'tpms_msk.nii.gz' ]
+    >>> normalize.inputs.in_mask = 'tpms_msk.nii.gz'
     >>> normalize.run() # doctest: +SKIP
     """
     input_spec = NormalizeProbabilityMapSetInputSpec