diff --git a/moto/apigateway/models.py b/moto/apigateway/models.py
index 7707bd9d..d376db5c 100644
--- a/moto/apigateway/models.py
+++ b/moto/apigateway/models.py
@@ -610,12 +610,12 @@ class RestAPI(BaseModel):
         return self.deployments.pop(deployment_id)
 
 
-class DomainName(BaseModel,dict):
+class DomainName(BaseModel, dict):
     def __init__(self, domain_name, **kwargs):
         super(DomainName, self).__init__()
         self["domainName"] = domain_name
-        self["regionalDomainName"] = domain_name,
-        self["distributionDomainName"] = domain_name,
+        self["regionalDomainName"] = domain_name
+        self["distributionDomainName"] = domain_name
         self["domainNameStatus"] = "AVAILABLE"
         self["domainNameStatusMessage"] = "Domain Name Available"
         self["regionalHostedZoneId"] = "Z2FDTNDATAQYW2"
@@ -628,31 +628,21 @@ class DomainName(BaseModel,dict):
         if kwargs.get("certificate_body"):
             self["certificateBody"] = kwargs.get("certificate_body")
         if kwargs.get("tags"):
-            self["tags"] = kwargs.get("tags" )
+            self["tags"] = kwargs.get("tags")
         if kwargs.get("security_policy"):
             self["securityPolicy"] = kwargs.get("security_policy")
         if kwargs.get("certificate_chain"):
             self["certificateChain"] = kwargs.get("certificate_chain")
         if kwargs.get("regional_certificate_name"):
-            self["regionalCertificateName"] = kwargs.get(
-                "regional_certificate_name"
-            )
+            self["regionalCertificateName"] = kwargs.get("regional_certificate_name")
         if kwargs.get("certificate_private_key"):
-            self["certificatePrivateKey"] = kwargs.get(
-                "certificate_private_key"
-            )
+            self["certificatePrivateKey"] = kwargs.get("certificate_private_key")
         if kwargs.get("regional_certificate_arn"):
-            self["regionalCertificateArn"] = kwargs.get(
-                "regional_certificate_arn"
-            )
+            self["regionalCertificateArn"] = kwargs.get("regional_certificate_arn")
         if kwargs.get("endpoint_configuration"):
-            self["endpointConfiguration"] = kwargs.get(
-                "endpoint_configuration"
-            )
+            self["endpointConfiguration"] = kwargs.get("endpoint_configuration")
         if kwargs.get("generate_cli_skeleton"):
-            self["generateCliSkeleton"] = kwargs.get(
-                "generate_cli_skeleton"
-            )
+            self["generateCliSkeleton"] = kwargs.get("generate_cli_skeleton")
 
 
 class APIGatewayBackend(BaseBackend):
@@ -1048,16 +1038,21 @@ class APIGatewayBackend(BaseBackend):
         except Exception:
             return False
 
-    def create_domain_name(self,domain_name,
-                           certificate_name=None,certificate_private_key=None,
-                           tags=None, certificate_arn=None,
-                           certificate_body=None,
-                           certificate_chain=None,
-                           regional_certificate_name=None,
-                           regional_certificate_arn=None,
-                           endpoint_configuration=None,
-                           security_policy=None,
-                           generate_cli_skeleton=None):
+    def create_domain_name(
+        self,
+        domain_name,
+        certificate_name=None,
+        tags=None,
+        certificate_arn=None,
+        certificate_body=None,
+        certificate_private_key=None,
+        certificate_chain=None,
+        regional_certificate_name=None,
+        regional_certificate_arn=None,
+        endpoint_configuration=None,
+        security_policy=None,
+        generate_cli_skeleton=None,
+    ):
 
         if not domain_name:
             raise InvalidDomainName()
@@ -1072,7 +1067,8 @@ class APIGatewayBackend(BaseBackend):
             regional_certificate_name=regional_certificate_name,
             regional_certificate_arn=regional_certificate_arn,
             endpoint_configuration=endpoint_configuration,
-            tags=tags, security_policy=security_policy,
+            tags=tags,
+            security_policy=security_policy,
             generate_cli_skeleton=generate_cli_skeleton,
         )
 
diff --git a/moto/apigateway/responses.py b/moto/apigateway/responses.py
index ec05c605..e27982b2 100644
--- a/moto/apigateway/responses.py
+++ b/moto/apigateway/responses.py
@@ -546,8 +546,7 @@ class APIGatewayResponse(BaseResponse):
                 certificate_body = self._get_param("certificateBody")
                 certificate_private_key = self._get_param(
                     "certificatePrivateKey"
-                        )
-
+                )
                 certificate_chain = self._get_param("certificateChain")
                 regional_certificate_name = self._get_param(
                     "regionalCertificateName"
@@ -563,12 +562,18 @@ class APIGatewayResponse(BaseResponse):
                     "generateCliSkeleton"
                 )
                 domain_name_resp = self.backend.create_domain_name(
-                    domain_name, certificate_name,
-                    certificate_private_key,tags, certificate_arn,
-                    certificate_body,  certificate_chain,
-                    regional_certificate_name, regional_certificate_arn,
-                    endpoint_configuration, security_policy,
-                    generate_cli_skeleton
+                    domain_name,
+                    certificate_name,
+                    tags,
+                    certificate_arn,
+                    certificate_body,
+                    certificate_private_key,
+                    certificate_chain,
+                    regional_certificate_name,
+                    regional_certificate_arn,
+                    endpoint_configuration,
+                    security_policy,
+                    generate_cli_skeleton,
                 )
                 return 200, {}, json.dumps(domain_name_resp)
 
@@ -592,7 +597,6 @@ class APIGatewayResponse(BaseResponse):
                 if domain_name is not None:
                     domain_names = self.backend.get_domain_name(domain_name)
             return 200, {}, json.dumps(domain_names)
-
         except DomainNameNotFound as error:
             return (
                 error.code,
@@ -603,3 +607,4 @@ class APIGatewayResponse(BaseResponse):
             )
 
 
+
diff --git a/tests/test_apigateway/test_apigateway.py b/tests/test_apigateway/test_apigateway.py
index accd0fad..ec1049ac 100644
--- a/tests/test_apigateway/test_apigateway.py
+++ b/tests/test_apigateway/test_apigateway.py
@@ -1490,10 +1490,11 @@ def test_create_domain_names():
     test_certificate_name = "test.certificate"
     test_certificate_private_key = "testPrivateKey"
     # success case with valid params
-    response = client.create_domain_name(domainName=domain_name,
-                        certificateName=test_certificate_name,
-                        certificatePrivateKey=test_certificate_private_key)
-
+    response = client.create_domain_name(
+        domainName=domain_name,
+        certificateName=test_certificate_name,
+        certificatePrivateKey=test_certificate_private_key,
+    )
     response["domainName"].should.equal(domain_name)
     response["certificateName"].should.equal(test_certificate_name)
     # without domain name it should throw BadRequestException