Django - Python 3 - "AssertionError: A model can't have more than one AutoField."

From docs:

By default, Django gives each model the following field:

id = models.AutoField(primary_key=True)

This is an auto-incrementing primary key.

If you’d like to specify a custom primary key, just specify primary_key=True on one of your fields. If Django sees you’ve explicitly set Field.primary_key, it won’t add the automatic id column.

Each model requires exactly one field to have primary_key=True (either explicitly declared or automatically added).

So try to set primary_key=True like this:

bid = models.AutoField(db_column='BID', primary_key=True)