<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def drop_index(self, model, *columns):
 """Drop indexes."""

        columns_ = []
        for col in columns:
            field = model._meta.fields.get(col)
            if not field:
                continue

            if len(columns) == 1:
                field.unique = field.index = False

            if isinstance(field, pw.ForeignKeyField):
                col = col + '_id'
            columns_.append(col)
        index_name = make_index_name(model._meta.table_name, columns_)
        model._meta.indexes = [(cols, _) for (cols, _) in model._meta.indexes if columns != cols]
        self.ops.append(self.migrator.drop_index(model._meta.table_name, index_name))
        return model