contentType := r.Header.Get("Content-Type")
		if contentType == "application/json" {
			w.Header().Set("Content-Type", "application/json")
			jsonEncoder := json.NewEncoder(w)
			jsonEncoder.Encode(metrics)
			return
		}

		// If not JSON, return plain text. We format it as a markdown table for
		// readability.
		w.Header().Set("Content-Type", "text/plain")

* Fix encoding of Pydantic models that inherit from others models with custom `json_encoders`. PR [#1769](https://github.com/tiangolo/fastapi/pull/1769) by [@henrybetts](https://github.com/henrybetts).