incorporated feedback on pull request mne-tools#13759 again

Author: chsquare

mne/channels/interpolation.py

@@ -490,28 +490,24 @@ def _interpolate_to_meg(inst, sensors, origin, mode):
     # Get source MEG info
     info_from = pick_info(inst.info, picks_meg_good)
 
-    # Design target info like source, except for channel info and
-    # some (possibly) related fields
+    # Update target info to accommodate the desired channel info
+    # and reset some channel and machine-related fields to avoid
+    # confusion later on.
+    # NOTE: We don't change the original 'dev_head_t'.
+    #       Some keys require as default an empty list.
     info_to = deepcopy(info_from)
-    info_to._unlocked = True  # make all info fields modifiable
-    # Update channel info to the desired one
-    info_to["chs"] = deepcopy(info_cano["chs"])
-    info_to["ch_names"] = deepcopy(info_cano["ch_names"])
-    info_to["nchan"] = deepcopy(info_cano["nchan"])
-    # Reset some channel and machine-related fields to avoid confusion later on
-    info_to["device_info"] = None
-    info_to["helium_info"] = None
-    info_to["proj_id"] = None
-    info_to["proj_name"] = None
-    info_to["gantry_angle"] = None
-    # we keep original 'dev_head_t'
-    info_to["ctf_head_t"] = None
-    info_to["dev_ctf_t"] = None
-    # info_to['dig'] = None  # or should they be removed, too?
-    info_to["bads"] = []
-    info_to["projs"] = []
-    info_to["comps"] = []
-    info_to._unlocked = False  # lock info again
+    with info_to._unlock():
+        info_to.update({"chs": deepcopy(info_cano["chs"]),
+                        "ch_names": deepcopy(info_cano["ch_names"]),
+                        "nchan": deepcopy(info_cano["nchan"]),
+                        "device_info": None,
+                        "helium_info": None,
+                        "gantry_angle": None,
+                        "ctf_head_t": None,
+                        "dev_ctf_t": None,
+                        "bads": [],
+                        "projs": [],
+                        "comps": []})
 
     # Compute field interpolation mapping
     origin_val = _check_origin(origin, inst.info)