peewee.ModelBase has no attribute 'bulk_update'
```python
In [1]: from peewee import *                                                                    

In [2]: class MyModel(Model): 
   ...:     pass 
   ...:                                                                                         

In [3]: MyModel.bulk_update                                                                     
Out[3]: <bound method Model.bulk_update of <Model: MyModel>>
```
As you can see below, when l print type of the peewee model, l get **<class 'peewee.ModelBase'>**
However,  it complains bulk_update does not exist. Also running dir on the Model class, does not contain the **bulk_update**

[2020-10-12 08:20:36,241] {test.py:250} INFO - <class 'peewee.ModelBase'>
[2020-10-12 08:30:35,533] {test.py:251} INFO - ['DoesNotExist', '__class__', '__data__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__rel__', '__repr__', '__setattr__', '__sizeof__', '__sql__', '__str__', '__subclasshook__', '__weakref__', '_as_dict', '_coerce', '_meta', '_normalize_data', '_pk', '_pk_expr', '_populate_unsaved_relations', '_prune_fields', '_schema', "'bulk_create'']
[2020-10-12 08:30:35,533] {taskinstance.py:1150} ERROR - type object 'Study' has no attribute 'bulk_update'
[2020-10-12 08:20:36,241] {test.py:1150} ERROR - type object 'Study' has no attribute 'bulk_update'

What could be the issue?