feat: add type hints to Client (#2044)

* add type hints

* Update client.py

Moves import from being used solely during specific checks to being more universally available.

* Update google/cloud/bigquery/client.py

* Update client.py

testing some minor changes to deal with mypy quirks

* Update google/cloud/bigquery/client.py

---------

Co-authored-by: Chalmer Lowe <[email protected]>

Author: rinarakaki

google/cloud/bigquery/client.py

@@ -44,6 +44,8 @@
 import uuid
 import warnings
 
+import requests
+
 from google import resumable_media  # type: ignore
 from google.resumable_media.requests import MultipartUpload  # type: ignore
 from google.resumable_media.requests import ResumableUpload
@@ -65,6 +67,7 @@
     DEFAULT_BQSTORAGE_CLIENT_INFO = None  # type: ignore
 
 
+from google.auth.credentials import Credentials
 from google.cloud.bigquery._http import Connection
 from google.cloud.bigquery import _job_helpers
 from google.cloud.bigquery import _pandas_helpers
@@ -126,15 +129,14 @@
     _versions_helpers.PANDAS_VERSIONS.try_import()
 )  # mypy check fails because pandas import is outside module, there are type: ignore comments related to this
 
+
 ResumableTimeoutType = Union[
     None, float, Tuple[float, float]
 ]  # for resumable media methods
 
 if typing.TYPE_CHECKING:  # pragma: NO COVER
     # os.PathLike is only subscriptable in Python 3.9+, thus shielding with a condition.
     PathType = Union[str, bytes, os.PathLike[str], os.PathLike[bytes]]
-    import requests  # required by api-core
-
 _DEFAULT_CHUNKSIZE = 100 * 1024 * 1024  # 100 MB
 _MAX_MULTIPART_SIZE = 5 * 1024 * 1024
 _DEFAULT_NUM_RETRIES = 6
@@ -231,30 +233,34 @@ class Client(ClientWithProject):
 
     def __init__(
         self,
-        project=None,
-        credentials=None,
-        _http=None,
-        location=None,
-        default_query_job_config=None,
-        default_load_job_config=None,
-        client_info=None,
-        client_options=None,
+        project: Optional[str] = None,
+        credentials: Optional[Credentials] = None,
+        _http: Optional[requests.Session] = None,
+        location: Optional[str] = None,
+        default_query_job_config: Optional[QueryJobConfig] = None,
+        default_load_job_config: Optional[LoadJobConfig] = None,
+        client_info: Optional[google.api_core.client_info.ClientInfo] = None,
+        client_options: Optional[
+            Union[google.api_core.client_options.ClientOptions, Dict[str, Any]]
+        ] = None,
     ) -> None:
+        if client_options is None:
+            client_options = {}
+        if isinstance(client_options, dict):
+            client_options = google.api_core.client_options.from_dict(client_options)
+        # assert isinstance(client_options, google.api_core.client_options.ClientOptions)
+
         super(Client, self).__init__(
             project=project,
             credentials=credentials,
             client_options=client_options,
             _http=_http,
         )
 
-        kw_args = {"client_info": client_info}
+        kw_args: Dict[str, Any] = {"client_info": client_info}
         bq_host = _get_bigquery_host()
         kw_args["api_endpoint"] = bq_host if bq_host != _DEFAULT_HOST else None
         client_universe = None
-        if client_options is None:
-            client_options = {}
-        if isinstance(client_options, dict):
-            client_options = google.api_core.client_options.from_dict(client_options)
         if client_options.api_endpoint:
             api_endpoint = client_options.api_endpoint
             kw_args["api_endpoint"] = api_endpoint