diff --git a/src/zeep/client.py b/src/zeep/client.py
index fac7ecd7..79f203cf 100644
--- a/src/zeep/client.py
+++ b/src/zeep/client.py
@@ -55,13 +55,13 @@ class Client:
 
     def __init__(
         self,
-        wsdl,
+        wsdl: typing.Union[typing.IO, str],
         wsse=None,
         transport=None,
         service_name=None,
         port_name=None,
         plugins=None,
-        settings=None,
+        settings: typing.Optional[Settings] = None,
     ):
         if not wsdl:
             raise ValueError("No URL given for the wsdl")
diff --git a/src/zeep/exceptions.py b/src/zeep/exceptions.py
index 632b3b08..231fb594 100644
--- a/src/zeep/exceptions.py
+++ b/src/zeep/exceptions.py
@@ -1,5 +1,5 @@
 class Error(Exception):
-    def __init__(self, message=""):
+    def __init__(self, message: str = ""):
         super(Exception, self).__init__(message)
         self.message = message
 
@@ -19,7 +19,7 @@ def __init__(self, *args, **kwargs):
         self.sourceline = kwargs.pop("sourceline", None)
         super().__init__(*args, **kwargs)
 
-    def __str__(self):
+    def __str__(self) -> str:
         location = None
         if self.filename and self.sourceline:
             location = "%s:%s" % (self.filename, self.sourceline)
@@ -37,7 +37,7 @@ class WsdlSyntaxError(Error):
 
 
 class TransportError(Error):
-    def __init__(self, message="", status_code=0, content=None):
+    def __init__(self, message: str = "", status_code=0, content=None):
         super().__init__(message)
         self.status_code = status_code
         self.content = content
@@ -56,7 +56,7 @@ class NamespaceError(Error):
 
 
 class Fault(Error):
-    def __init__(self, message, code=None, actor=None, detail=None, subcodes=None):
+    def __init__(self, message: str, code=None, actor=None, detail=None, subcodes=None):
         super().__init__(message)
         self.message = message
         self.code = code
@@ -74,7 +74,7 @@ def __init__(self, *args, **kwargs):
         self.path = kwargs.pop("path", [])
         super().__init__(*args, **kwargs)
 
-    def __str__(self):
+    def __str__(self) -> str:
         if self.path:
             path = ".".join(str(x) for x in self.path)
             return "%s (%s)" % (self.message, path)
diff --git a/src/zeep/transports.py b/src/zeep/transports.py
index ffde356b..98f94f66 100644
--- a/src/zeep/transports.py
+++ b/src/zeep/transports.py
@@ -4,7 +4,7 @@
 from urllib.parse import urlparse
 
 import requests
-from requests import Response
+from requests import Response as Response
 from requests_file import FileAdapter
 
 from zeep.exceptions import TransportError
diff --git a/src/zeep/wsdl/wsdl.py b/src/zeep/wsdl/wsdl.py
index f842fa43..cd200590 100644
--- a/src/zeep/wsdl/wsdl.py
+++ b/src/zeep/wsdl/wsdl.py
@@ -61,7 +61,11 @@ class Document:
     """
 
     def __init__(
-        self, location, transport: typing.Type["Transport"], base=None, settings=None
+        self,
+        location: typing.Union[typing.IO, str],
+        transport: typing.Type["Transport"],
+        base=None,
+        settings=None
     ):
         """Initialize a WSDL document.