How to define custom permissions for user creating task?

[Praveen chaduvala]

how to give custom permission for creating task 

example my model defined two types of fields 

1.Doctor model

doctor model contating is_doctor field 

2.Patient model

patient model containing Is_patient field

when i am creating some tasks patient token also creating doctors tasks

go through

my code:

django - How to Create custom permission classes? - Stack Overflow 

https://stackoverflow.com/users/11869457/prashanth