Fix duplicates in gds with multiple top-level cells

Since the different patterns we are handed might reference the same
Patterns, we have to deepcopy the entire list at once so that we
don't make multiple copies of them.

masque/file/gdsii.py

@@ -90,7 +90,7 @@ def write(patterns: Pattern or List[Pattern],
         disambiguate_func = disambiguate_pattern_names
 
     if not modify_originals:
-        patterns = [p.deepcopy().deepunlock() for p in patterns]
+        patterns = [p.deepunlock() for p in copy.deepcopy(patterns)]
 
     # Create library
     lib = gdsii.library.Library(version=600,