Shallow copy track in smoothers

[sdhiscocks]

Resolves #1125

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.70%. Comparing base (9393fe7) to head (12b962f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1126      +/-   ##
==========================================
- Coverage   93.72%   93.70%   -0.03%     
==========================================
  Files         217      217              
  Lines       14430    14431       +1     
  Branches     1963     1963              
==========================================
- Hits        13525    13522       -3     
- Misses        644      646       +2     
- Partials      261      263       +2     

Flag	Coverage Δ
integration	65.60% <33.33%> (+0.03%)	⬆️
unittests	91.00% <100.00%> (-0.03%)	⬇️

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[sglvladi]

This may have the (undesirable?) effect of changes in the original track's metadata being inadvertently reflected in the smoothed track's metadata.

[sdhiscocks]

Could also add shallow copy of the dictionaries of meta data?

diff --git a/stonesoup/types/tests/test_track.py b/stonesoup/types/tests/test_track.py
index 9c226e78..9ca8754b 100644
--- a/stonesoup/types/tests/test_track.py
+++ b/stonesoup/types/tests/test_track.py
@@ -201,7 +201,7 @@ def test_copy():
         assert original_state is copied_state
 
     for original_metadata, copied_metadata in zip(track.metadatas, copied_track.metadatas):
-        assert original_metadata is copied_metadata
+        assert original_metadata == copied_metadata
 
     assert len(track) == 3
     assert len(copied_track) == 3
diff --git a/stonesoup/types/track.py b/stonesoup/types/track.py
index 5a904b85..45f8b9fc 100644
--- a/stonesoup/types/track.py
+++ b/stonesoup/types/track.py
@@ -50,7 +50,7 @@ class Track(StateMutableSequence):
 
     def __copy__(self):
         inst = super().__copy__()
-        inst.__dict__['metadatas'] = copy.copy(self.__dict__['metadatas'])
+        inst.__dict__['metadatas'] = list(copy.copy(md) for md in self.__dict__['metadatas'])
         return inst
 
     def insert(self, index, value):

I think this is reasonable to be part of shallow copy as well, as Track object is already manipulating and copying these dictionaries itself when states are added/removed.