diff --git a/.github/workflows/tests.yaml b/.github/workflows/tests.yaml
index 7173abc..4d1a936 100644
--- a/.github/workflows/tests.yaml
+++ b/.github/workflows/tests.yaml
@@ -17,7 +17,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.7", "3.8", "3.9", "3.10", "3.11"]
+        python-version: ["3.8", "3.9", "3.10", "3.11"]
         os: [ubuntu-latest, macos-latest, windows-latest]
     steps:
       - uses: actions/checkout@v3
diff --git a/docker-compose.yml b/docker-compose.yml
new file mode 100644
index 0000000..90dfd60
--- /dev/null
+++ b/docker-compose.yml
@@ -0,0 +1,12 @@
+version: '3.5'
+
+services:
+
+  graphene_federation:
+    container_name: pydantic
+    build:
+      context: .
+    environment:
+      - TERM=xterm-256color
+    volumes:
+      - ./:/workdir
diff --git a/graphene_pydantic/converters.py b/graphene_pydantic/converters.py
index 35b9853..1e3297c 100644
--- a/graphene_pydantic/converters.py
+++ b/graphene_pydantic/converters.py
@@ -24,12 +24,13 @@
     UUID,
     Union,
 )
+from graphene.types.base import BaseType
 from graphene.types.datetime import Date, DateTime, Time
 from pydantic import BaseModel
 from pydantic.fields import FieldInfo
 from pydantic_core import PydanticUndefined
 
-from .registry import Registry
+from .registry import Placeholder, Registry
 from .util import construct_union_class_name, evaluate_forward_ref
 
 PYTHON10 = sys.version_info >= (3, 10)
@@ -175,7 +176,7 @@ def convert_pydantic_type(
     registry: Registry,
     parent_type: T.Type = None,
     model: T.Type[BaseModel] = None,
-) -> Type:  # noqa: C901
+) -> T.Union[Type[T.Union[BaseType, List]], Placeholder]:  # noqa: C901
     """
     Convert a Pydantic type to a Graphene Field type, including not just the
     native Python type but any additional metadata (e.g. shape) that Pydantic
@@ -197,7 +198,7 @@ def find_graphene_type(
     registry: Registry,
     parent_type: T.Type = None,
     model: T.Type[BaseModel] = None,
-) -> Type:  # noqa: C901
+) -> T.Union[Type[T.Union[BaseType, List]], Placeholder]:  # noqa: C901
     """
     Map a native Python type to a Graphene-supported Field type, where possible,
     throwing an error if we don't know what to map it to.
@@ -303,10 +304,10 @@ def convert_generic_python_type(
     registry: Registry,
     parent_type: T.Type = None,
     model: T.Type[BaseModel] = None,
-) -> Type:  # noqa: C901
+) -> T.Union[Type[T.Union[BaseType, List]], Placeholder]:  # noqa: C901
     """
     Convert annotated Python generic types into the most appropriate Graphene
-    Field type -- e.g. turn `typing.Union` into a Graphene Union.
+    Field type -- e.g., turn `typing.Union` into a Graphene Union.
     """
     origin = type_.__origin__
     if not origin:  # pragma: no cover  # this really should be impossible
@@ -393,7 +394,7 @@ def convert_literal_type(
     registry: Registry,
     parent_type: T.Type = None,
     model: T.Type[BaseModel] = None,
-):
+) -> T.Union[Type[T.Union[BaseType, List]], Placeholder]:
     """
     Convert an annotated Python Literal type into a Graphene Scalar or Union of Scalars.
     """
diff --git a/graphene_pydantic/inputobjecttype.py b/graphene_pydantic/inputobjecttype.py
index 01b7587..95f444d 100644
--- a/graphene_pydantic/inputobjecttype.py
+++ b/graphene_pydantic/inputobjecttype.py
@@ -80,8 +80,8 @@ def __init_subclass_with_meta__(
         _meta=None,
         **options,
     ):
-        assert (
-            model and issubclass(model, pydantic.BaseModel)
+        assert model and issubclass(
+            model, pydantic.BaseModel
         ), f'You need to pass a valid Pydantic model in {cls.__name__}.Meta, received "{model}"'
 
         assert isinstance(
diff --git a/graphene_pydantic/objecttype.py b/graphene_pydantic/objecttype.py
index 1f36abd..91f6bbd 100644
--- a/graphene_pydantic/objecttype.py
+++ b/graphene_pydantic/objecttype.py
@@ -71,8 +71,8 @@ def __init_subclass_with_meta__(
         _meta=None,
         **options,
     ):
-        assert (
-            model and issubclass(model, pydantic.BaseModel)
+        assert model and issubclass(
+            model, pydantic.BaseModel
         ), f'You need to pass a valid Pydantic model in {cls.__name__}.Meta, received "{model}"'
 
         assert isinstance(
diff --git a/graphene_pydantic/registry.py b/graphene_pydantic/registry.py
index 1bc99b8..362f2a2 100644
--- a/graphene_pydantic/registry.py
+++ b/graphene_pydantic/registry.py
@@ -2,6 +2,7 @@
 from collections import defaultdict
 from typing import Dict, Generic, Optional, Type, TypeVar, Union
 
+from graphene.types.base import BaseType
 from pydantic import BaseModel
 from pydantic.fields import FieldInfo
 
@@ -39,7 +40,7 @@ class Registry(Generic[T]):
 
     def __init__(self, required_obj_type: ObjectType):
         self._required_obj_type: ObjectType = required_obj_type
-        self._registry: Dict[ModelType, Output] = {}
+        self._registry: Dict[ModelType, Union[Type[BaseType], Placeholder]] = {}
         self._registry_object_fields: Dict[
             ObjectType, Dict[str, FieldInfo]
         ] = defaultdict(dict)
@@ -52,7 +53,9 @@ def register(self, obj_type: ObjectType):
         ), "Can't register models linked to another Registry"
         self._registry[obj_type._meta.model] = obj_type
 
-    def get_type_for_model(self, model: ModelType) -> Optional[Output]:
+    def get_type_for_model(
+        self, model: ModelType
+    ) -> Union[Type[BaseType], Placeholder]:
         return self._registry.get(model)
 
     def add_placeholder_for_model(self, model: ModelType):
diff --git a/pyproject.toml b/pyproject.toml
index 4942549..2846d00 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -23,7 +23,7 @@ classifiers = [
 keywords = ["api", "graphql", "protocol", "rest", "relay", "graphene", "pydantic", "model"]
 
 [tool.poetry.dependencies]
-python = "^3.7"
+python = "^3.8"
 graphene = ">=2.1.8"
 pydantic = ">=2.0"