"TypeError: fromisoformat: argument must be str"

I have a model named vendor which have some fields when i enter other attributes in this model and run migrations it gave me this error “TypeError: fromisoformat: argument must be str” I have checked all attributes and their properties and change them but it still gives me this error.
After this error when i add any attributes in any model it is giving me this error and when i run “python manage.py runserver” command it shows me that you have (number) of unapplied migratoions.
I have try to delete the all migrations and make new migrations but it is not solving my problem.

My vendor model is this…

class Vendor(models.Model):
    user = models.ForeignKey(
    vendorName = models.TextField(null=True)
    vendorCNIC = models.CharField(max_length=15,default=None)
    vendorContact = models.CharField(max_length=15,default=None)
    vendorAddress = models.TextField(null=True)
    vendorCurrentBalance=models.DecimalField(max_digits=10, decimal_places=2, default=0.0)
    vendorOpeningBalance=models.DecimalField(max_digits=10, decimal_places=2, default=0.0)
    vendorOpeningBalanceDate=models.DateField(blank=True, null=True)

Is this issue related to DateField because i have added DateField in other models before but it will not gaves me any error but this time it gives me this error and when i try to add other attribute in different model it is giving me the same error…

Please post the complete traceback along with a more detailed description of what you mean by:

I want to add some attributes in vendor model but when i add and make migrations it shows me this error “TypeError: fromisoformat: argument must be str” and after this when i add attribute to any other model like customer,employee etc it gives me the same issue and migrations are not applying.

Side note: Please do not post messages that consist only of tagging specific individuals requesting help.

No, actually you haven’t.

This is not detailed:

You need to show the exact lines of code you’re trying to add, and identify which code was working, and what line of code being added starts to show the error.

Yes, please don’t tag me, I look at support forum posts when I can.