how can I solve keyerror when formatting string in pythong

Question

I just want the following outcome. But I get KeyError: '"msg_body"'.

input:

text="text"
uid="uid"
input = '{"msg_body":{input_text}, "user_id":{input_uid}}'.format(input_text=text, input_uid=test)

wanted output:

'{"msg_body":"text", "user_id":"uid"}'

Single or double quotations must be exactly how it is above. Thanks