Describe the Bug

If you try to make a strawberry type from a pydantic class but mask out one of the fields in the pydantic class by making it private, it produces a key error.

class MyPydanticClass(BaseModel):
a_field: int
b_field: int

@strawberry.experimental.pydantic.type(model=NewVrmOrder
class MyStrawberryClass(model=MyPydanticClass):
a_field: strawberry.auto
b_field: strawberry.Private[int]

Traceback (most recent call last):
File ".../example.py", line 11, in
class MyStrawberryClass:
File ".../python3.8/site-packages/strawberry/experimental/pydantic/object_type.py", line 175, in wrap
all_model_fields: List[DataclassCreationFields] = [
File ".../python3.8/site-packages/strawberry/experimental/pydantic/object_type.py", line 176, in
_build_dataclass_creation_fields(
File ".../python3.8/site-packages/strawberry/experimental/pydantic/object_type.py", line 63, in _build_dataclass_creation_fields
else existing_fields[field.name].type
KeyError: 'b_field'