chore(external_sources): Export externall sources

Author: ehdsouza

ibm_cloud_sdk_core/__init__.py

@@ -19,4 +19,4 @@
 from .jwt_token_manager import JWTTokenManager
 from .cp4d_token_manager import CP4DTokenManager
 from .api_exception import ApiException
-from .utils import datetime_to_string, string_to_datetime, get_authenticator_from_environment
+from .utils import datetime_to_string, string_to_datetime, get_authenticator_from_environment, read_external_sources