Generate Graphql schema without paths

[naulacambra]

Describe the bug
I have an OpenAPI definition, Master-OB-OpenAPI.json, which doesn't have any path in it, only schema definitions. I've tried to generate the Graphql schema file, but it only generated this

schema {
  query: QueryPlaceholder
}

"""Placeholder object"""
type QueryPlaceholder {
  """Placeholder field"""
  message: String
}

To Reproduce
Steps to reproduce the behavior:

1. Execute npx openapi-to-graphql .\Master-OB-OpenAPI.json --save output.sdl
2. Inspect the output.sdl file
3. See the output written above

Expected behavior
I would expected an sdl file with all the schemas in it