What validator is needed to check type and size in MultipleFileField?

Question

Python

I'm making a form to upload multiple images at once.
I don't know which validator to check if the selected files are images,
and also if they are larger than a certain size.

from flask_wtf import FlaskForm
from wtforms import SubmitField, MultipleFileField
from wtforms.validators import Required


class UploadImagesForm(FlaskForm):
    images = MultipleFileField('Upload images', validators=[Required()])
    submit = SubmitField('Upload')

Answer 1

own validator.