Django (1, 4, 0, 'alpha', 0): Trying to get custom model field to pass custom attribute to form (and eventually a widget)... What am I doing wrong here?

admin.py

from django.contrib import admin
from test.models import Test

admin.site.register(Test)

fields.py

from django.db import models
from test import forms

class TestField(models.CharField):
    
    """
    Docstring...
    """
    
    description = 'Description...'
    
    def __init__(self, baz=None, *args, **kwargs):
#     def __init__(self, *args, **kwargs):
        
        # Get model kwarg (is this the best place to set default values?):
#         self._baz = kwargs.get('baz', None) # TypeError: __init__() got an unexpected keyword argument 'baz'
        
        self._baz = baz
        
        super(TestField, self).__init__(*args, **kwargs)
    
    def formfield(self, **kwargs):
        
        # Set kwarg defaults:
        defaults = {
            'baz': _baz,
            'form_class': forms.TestField,
        }
        
        # Update kwargs with defaults:
        defaults.update(kwargs)
        
        return super(TestField, self).formfield(**defaults)

forms.py

from django.forms import fields
# from test import widgets

class TestField(fields.CharField):
    
    """
    Docstring...
    """
    
    description = 'Description...'
    
    def __init__(self, baz=None, *args, **kwargs):
        
        # Or this?
#         self.baz = kwargs.get('baz', None)
        
        # Call the widget:
#         self.widget = widgets.TestWidget(baz=baz, **kwargs)
        
        # Default kwargs:
        dwargs = {
            'required': True,
            'label': None,
            'initial': None,
            'help_text': None,
            'error_messages': None,
            'show_hidden_initial': False,
        }
        
        # Assign attribute values from kwargs to dwargs:
        for attr in dwargs:
            if attr in kwargs:
                dwargs[attr] = kwargs[attr]
        
        super(TestField, self).__init__(*args, **dwargs)
    
    def clean(self, value):
        
        # Do stuff with value here.
        
        pass

models.py

from django.db import models
from test.fields import TestField

class Test(models.Model):
    
    """
    Docstring...
    """
    
    description = 'Description...'
    
    foo = TestField(u'Foo field', baz='bar', max_length=100, help_text='Foo baz bar?')
    
    # I've hit a brick wall here:
    # __init__() got multiple values for keyword argument 'baz'
    # In line #12 above. :(

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