FIX: DigMontage.rename_channels should return self (#13320)

Author: sappelhoff

doc/changes/v1.10.rst

@@ -50,6 +50,7 @@ Bugfixes
 - Fix y-axis label in PSD plot when ``dB=True`` to show a more conventional label (i.e., dB/Hz or dB/√Hz), by `Clemens Brunner`_. (`#13298 <https://github.com/mne-tools/mne-python/pull/13298>`__)
 - Fix bug in :func:`mne.sys_info` where calling it in Windows could lead to a an error while trying to get the amount of available memory, by `Eric Larson`_. (`#13310 <https://github.com/mne-tools/mne-python/pull/13310>`__)
 - Change default pupil unit scalings from micrometrs to millimeters by `Scott Huberty`_ (`#13314 <https://github.com/mne-tools/mne-python/pull/13314>`__)
+- Fix :meth:`mne.channels.DigMontage.rename_channels` so that the changed montage is returned instead of ``None``, by `Stefan Appelhoff`_. (`#13320 <https://github.com/mne-tools/mne-python/pull/13320>`__)
 
 
 API changes by deprecation

mne/channels/montage.py

@@ -397,6 +397,7 @@ def rename_channels(self, mapping, allow_duplicates=False):
         temp_info = create_info(list(self._get_ch_pos()), 1000.0, "eeg")
         rename_channels(temp_info, mapping, allow_duplicates)
         self.ch_names = temp_info["ch_names"]
+        return self
 
     @verbose
     def save(self, fname, *, overwrite=False, verbose=None):
@@ -720,7 +721,7 @@ def transform_to_head(montage):
     Returns
     -------
     montage : instance of DigMontage
-        The montage after transforming the points to head
+        A copy of the montage after transforming the points to head
         coordinate system.
 
     Notes

mne/channels/tests/test_montage.py

@@ -1429,7 +1429,7 @@ def renamer(x):
             except ValueError:
                 return x
 
-        mon.rename_channels(renamer)
+        mon = mon.rename_channels(renamer)
         raw.set_montage(mon)
 
     if mon is not None:

mne/utils/docs.py

@@ -2037,7 +2037,7 @@ def _reflow_param_docstring(docstring, has_first_line=True, width=75):
 >>> mon = mne.channels.make_standard_montage('standard_1020')
 >>> need = 'S1 D1 S2 D2 S3 D3 S4 D4 S5 D5 S6 D6 S7 D7 S8'.split()
 >>> have = 'F3 FC3 C3 CP3 P3 F5 FC5 C5 CP5 P5 F7 FT7 T7 TP7 P7'.split()
->>> mon.rename_channels(dict(zip(have, need)))
+>>> mon.rename_channels(dict(zip(have, need)))  # doctest: +SKIP
 >>> raw.set_montage(mon)  # doctest: +SKIP
 
 The 3x3 (ETG-100) is laid out as two separate layouts::