Check that function does not return Any value [no-any-return]

If you use —warn-return-any, mypy generates an error if you return avalue with an Any type in a function that is annotated to return anon-Any value.

Example:

# mypy: warn-return-any
 
def fields(s):
     return s.split(',')
 
def first_field(x: str) -> str:
    # Error: Returning Any from function declared to return "str"  [no-any-return]
    return fields(x)[0]