# Buggy code
def print_schema(schema: GraphQLSchema) -> str:
    return print_filtered_schema(
        schema, lambda n: not is_specified_directive(n), is_defined_type
    )


# Traceback (AttributeError)
Traceback (most recent call last):
File "/home/ignormies/.local/share/virtualenvs/gql-bf-XGX4szKA-py3.8/lib/python3.8/site-packages/graphql/type/definition.py", line 735, in fields
fields = resolve_thunk(self._fields)
File "/home/ignormies/.local/share/virtualenvs/gql-bf-XGX4szKA-py3.8/lib/python3.8/site-packages/graphql/type/definition.py", line 293, in resolve_thunk
return thunk() if callable(thunk) else thunk
File "/home/ignormies/.local/share/virtualenvs/gql-bf-XGX4szKA-py3.8/lib/python3.8/site-packages/strawberry/type.py", line 133, in <lambda>
lambda types_replacement_map=None: _get_fields(wrapped, types_replacement_map),
File "/home/ignormies/.local/share/virtualenvs/gql-bf-XGX4szKA-py3.8/lib/python3.8/site-packages/strawberry/type.py", line 76, in _get_fields
fields[field_name] = field(
File "/home/ignormies/.local/share/virtualenvs/gql-bf-XGX4szKA-py3.8/lib/python3.8/site-packages/strawberry/field.py", line 315, in field
return field(wrap)
File "/home/ignormies/.local/share/virtualenvs/gql-bf-XGX4szKA-py3.8/lib/python3.8/site-packages/strawberry/field.py", line 171, in __call__
setattr(wrap, IS_STRAWBERRY_FIELD, True)
AttributeError: 'method' object has no attribute '_is_strawberry_field'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/home/ignormies/.config/JetBrains/PyCharm2020.1/scratches/scratch_7.py", line 30, in <module>
schema = strawberry.Schema(query=Query)
File "/home/ignormies/.local/share/virtualenvs/gql-bf-XGX4szKA-py3.8/lib/python3.8/site-packages/strawberry/schema.py", line 25, in __init__
super().__init__(
File "/home/ignormies/.local/share/virtualenvs/gql-bf-XGX4szKA-py3.8/lib/python3.8/site-packages/graphql/type/schema.py", line 205, in __init__
collect_referenced_types(query)
File "/home/ignormies/.local/share/virtualenvs/gql-bf-XGX4szKA-py3.8/lib/python3.8/site-packages/graphql/type/schema.py", line 382, in collect_referenced_types
for field in named_type.fields.values():
File "/usr/lib/python3.8/functools.py", line 967, in __get__
val = self.func(instance)
File "/home/ignormies/.local/share/virtualenvs/gql-bf-XGX4szKA-py3.8/lib/python3.8/site-packages/graphql/type/definition.py", line 737, in fields
raise TypeError(f"{self.name} fields cannot be resolved. {error}")
TypeError: Query fields cannot be resolved. 'method' object has no attribute '_is_strawberry_field'

Process finished with exit code 1

# Fixed code
def print_schema(schema: BaseSchema) -> str:
    graphql_core_schema = schema._schema  # type: ignore

    directives = filter(
        lambda n: not is_specified_directive(n), graphql_core_schema.directives
    )
    type_map = graphql_core_schema.type_map

    types = filter(is_defined_type, map(type_map.get, sorted(type_map)))  # type: ignore

    return "\n\n".join(
        chain(
            filter(None, [print_schema_definition(graphql_core_schema)]),
            (print_directive(directive) for directive in directives),
            (_print_type(type_, schema) for type_ in types),  # type: ignore
        )
    )