[Answer]-Ajax-based Django MultipleChoiceField

Yup here it is django-ajax-selects. Or select2 is also a good library to work with.

some_field = forms.MultipleChoiceField(
        choices=SOMECHOICE,
        widget=forms.SelectMultiple(),
        help_text='',
        label='',
        required=True,
        error_messages={'required': "This field is required (by default the value should be 'DEFAULT')."},
    )