code: def test_empty_schema(app, client, schema):
      @app.route("/foo")
      @app.output(schema, status_code=204)
      def empty_reposonse():
          return ""
  
      @app.route("/bar")
      @app.output(schema, content_type="image/png")
      def empty_schema():
          return ""
  
      rv = client.get("/openapi.json")
      assert rv.status_code == 200
      validate_spec(rv.json)
      assert (
          "content"
          not in rv.json["paths"]["/foo"]["get"]["responses"]["204"]
      )
  
      assert (
          "content"
          in rv.json["paths"]["/bar"]["get"]["responses"]["200"]
      )
      assert (
          rv.json["paths"]["/bar"]["get"]["responses"]["200"][
              "content"
          ]["image/png"]["schema"]
          == {}
      )
  
imports: import pytest
  from openapi_spec_validator import validate_spec
  from apiflask.schemas import EmptySchema
  from apiflask.schemas import FileSchema
label_desc: Use image node_id 3 for calling a global function with example usage: test_empty_schema(app, client, schema) and returns: str, str