HOTFIX: Python 3.9 does not support type list (#203)

* Update version.txt

* Update README.md

* chore: Update `convert_to_expected_type` function signature

* chore: Mock config in unit tests for TestHelpersFunctions

* undo a change

* HOTFIX: Python <3.9 does not support type list

helpers.py

@@ -45,8 +45,8 @@ def get_value_by_path(meter_data: dict, path):
     return value
 
 
-def convert_to_expected_type(value: str, expected_type: list[str, int, float, bool],
-                             default: list[None, str, int, float, bool]) -> list[None, str, int, float, bool]:
+def convert_to_expected_type(value: str, expected_type: [str, int, float, bool],  # type: ignore
+                             default: [None, str, int, float, bool]) -> [None, str, int, float, bool]:  # type: ignore
     ''' Try to convert value to expected_type, otherwise return default'''
     try:
         conversion_functions = {