How to get the function result from ast.Call object?

I need to test the python dictionary in the python module without running the file. So I've decided to parse it with the ast.parse. I've almost figure out how to build the original dictionary except I can't find a way to get function values working.

config.py
...
config = {
    # theese None, booleans and strings I got parsed
    user_info: None,
    debug: False,
    cert_pass: "test",

    # the function values I have problem with
    project_directory: os.path.join(__file__, 'project')
}
...


test.py
...
# Skiping the AST parsing part, going straight to parsing config dict 

def parse_ast_dict(ast_dict):
   #ast_dict is instance of ast.Dict
   result_dict = {}
   # iterating over keys and values
   for item in zip(ast_dict.keys, ast_dict.values):
       if isinstance(item[1], ast.NameConstant):
           result_dict[item[0].s] = item[1].value
       elif isinstance(item[1], ast.Str):
           result_dict[item[0].s] = item[1].s
       elif isinstance(item[1], ast.Num):
           result_dict[item[0].s] = item[1].n

       # I got stuck here parsing the ast.Call which in my case is os.path.join calls
       elif isinstance(item[0].s, ast.Call):
           pass
   return result_dict

I can't move the config object to a different file so that I can test it in isolation because it's a vendor provided code piece and can't import it to the tests either because it contains a lot of library imports so I stuck with ast.

from How to get the function result from ast.Call object?