Improve unit-tests code coverage

patroni/collections.py

@@ -228,6 +228,11 @@ class _FrozenDict(Mapping[str, Any]):
         """Get the length of this dict.
 
         :returns: number of keys in the dict.
+
+        :Example:
+
+        >>> len(_FrozenDict())
+        0
         """
         return len(self.__values)
 

patroni/postgresql/available_parameters/__init__.py

@@ -1,12 +1,13 @@
 import logging
 import sys
 
-from pathlib import Path
 from typing import Iterator
 
 logger = logging.getLogger(__name__)
 
-if sys.version_info < (3, 9):
+if sys.version_info < (3, 9):  # pragma: no cover
+    from pathlib import Path
+
     PathLikeObj = Path
     conf_dir = Path(__file__).parent
 else: