When using string class names in ManyToManyField results in an error

[flaeppe]

When referencing a related model with ManyToManyField in a string, e.g.

class MyModel(models.Model):
    field = ManyToManyField("OtherModel")

An error can appear with a message looking something like:

error: Need type annotation for "field"  [var-annotated]

Make sure that you then use a format that includes the app label in the string e.g.

class MyModel(models.Model):
-    field = ManyToManyField("OtherModel")
+    field = ManyToManyField("myapp.OtherModel")

Doing the above should make the error go away.

Ref: #1802 (comment)