Incorrect optionality of attributes

The optionality of the attributes is not considered correctly. E.g. in the generated Swagger file, the Patient.gender is said to be required although the conformance statement doesn't. We used

fhir-swagger --fhir_url http://test.fhir.org/r3 --conformance_path="/metadata?_format=application/json" --dstu3 --output r3.json

and got

    ...
    "Patient": {
      "description": "",
      "type": "object",
      "properties": {
        ...
        "gender": {
          "type": "string",
          "minLength": 1
        },
        ...
      },
      "required": [
        "resourceType",
        "id",
        "text",
        "identifier",
        "active",
        "name",
        "gender",
        "photo",
        "contact",
        "managingOrganization",
        "link"
      ]
    },
    ...