Corrección error en Modelos

Se genera error al agregar un control medico a un carnet

Request Method: | POST
-- | --
http://127.0.0.1:5000/admin/carnets/control_medico/add/?_to_field=id&_popup=1
3.0.3
AttributeError
'Control_medico' object has no attribute 'ninio'
C:\Users\edyro\Desktop\dcarne\DCARNET\dcarnet\carnets\models.py in __str__, line 77
C:\Users\edyro\AppData\Local\Programs\Python\Python38-32\python.exe
3.8.1
['C:\\Users\\edyro\\Desktop\\dcarne\\DCARNET\\dcarnet', 'C:\\Users\\edyro\\AppData\\Local\\Programs\\Python\\Python38-32\\python38.zip', 'C:\\Users\\edyro\\AppData\\Local\\Programs\\Python\\Python38-32\\DLLs', 'C:\\Users\\edyro\\AppData\\Local\\Programs\\Python\\Python38-32\\lib', 'C:\\Users\\edyro\\AppData\\Local\\Programs\\Python\\Python38-32', 'C:\\Users\\edyro\\AppData\\Local\\Programs\\Python\\Python38-32\\lib\\site-packages']
Fri, 6 Mar 2020 18:24:47 +0000