Django resize thumbnail on save image

resize-thumbnail.py

from io import BytesIO
from os.path import splitext
from uuid import uuid4
from PIL import Image


def genereic_entity_upload_to(instance, filename):
    _, filename_ext = splitext(filename)
    return f"{instance.__class__.__name__}/{instance.entity.pk}/{uuid4()}.{filename_ext}".lower()


class EntityImage(Timestamp):
    image = models.FileField(
        "Image", upload_to=genereic_entity_upload_to, validators=[validate_ext_image],
        blank=True, null=True
    )
    title = models.CharField("Titulo", max_length=100, blank=True, null=True)
    summary = models.TextField("Resumo", blank=True, null=True)
    entity = models.ForeignKey(
        "core.Entity", on_delete=models.CASCADE, related_name="entity_images"
    )

    class Meta:
        verbose_name = "Entidade Image"
        verbose_name_plural = "Entidades Image"

    def __str__(self):
        return self.title

    def save(self, *args, **kwargs):
        buffer = BytesIO()
        THUMBNAIL_SIZE = (300, 300)

        image = Image.open(self.image.file)
        image.convert("RGB")
        image.thumbnail(THUMBNAIL_SIZE, Image.ANTIALIAS)

        filename, ext = splitext(self.image.name.strip())
        _format = ext.replace(".", "")

        if _format.lower() == "jpg":
            _format = "JPEG"

        image.save(buffer, format=_format)
        file_object = File(buffer)
        file_object.name = filename
        file_object.content_type = f"image/{ext.lower()}"
        self.image.save(f"{filename}.{ext}", file_object, save=False)
        super(EntityImage, self).save(*args, **kwargs)