getting error in flask while running the app

from flask import Flask, request
from flask.json import jsonify
 
app = Flask(__name__)

def predictions(solute, solvent):
    res = float(solute) + float(solvent)
    return res

@app.route('/predict', methods=["POST"])
def predict():

    solute = request.form.get('solute')
    solvent = request.form.get('solvent')
    result = predictions(solute, solvent)

    response = {}
    response["response"] = {
        'energy': str(result)
    }
    return jsonify(response)


if __name__ == '__main__':
    app.run(debug=True, host="0.0.0.0", port=3000)

{
    "response": {
        "energy": "13.8"
    }
}