I have problem with testing Google Cloud Function

This is my first time using Google Cloud Functions. And I have trouble with running the function. My code is like below.

import json
def location_sort(request):
    request = json.dumps(request)
    location = json.loads(request)
    reverse_location = {v: k for k, v in location.items()}



    x = location.keys()
    harf_x = (float(max(x)) + float(min(x))) / 2 

    y_right = []
    y_left = []
    sorted_location = [] 


    for i in location:
        if float(i) < harf_x:
            y_left.append(location[i])
        else: 
            y_right.append(location[i])

    y_left.sort() 
    y_right.sort(reverse=True) 

    sorted_input = y_left + y_right 


    for i in sorted_input:
        sorted_location.append([reverse_location[i], i])

    return json.dumps(sorted_location)

And i put in Trigger

{"38:127":"127.012","37.128":"127.002"} 

and the error shows up saying

Error: function terminated. Recommended action: inspect logs for termination reason. Details:
Object of type LocalProxy is not JSON serializable

How can I fix my problem?