UpdateView not saved

I try update my photo in avatar field but it not save changes, please look on it

update_form.html

{% extends 'base.html' %}
{% block title %}Edycja profilu{% endblock %}


{% if user.is_authenticated %}
    {% block top_menu %}
    <a href="{% url 'myprofile:profile-view' %}">{{ user.username }}</a>
    <a href="{% url 'users:logout-view' %}">Wyloguj się</a>
    {% endblock %}

{% block content %}
    <form action="" method="post">
        {% csrf_token %}
        {{ form.as_p }}
        <input type="submit" value="zapisz" />
    </form>
{% endblock %}
{% else %}

{% endif %}

views.py

from django.shortcuts import render
from django.views.generic import TemplateView, UpdateView
from users.models import MysiteUser

class ProfileView(TemplateView):
    template_name = 'profile.html'

class EditView(UpdateView):
    model = MysiteUser
    fields = ['avatar']
    pk_url_kwarg = 'pk'
    template_name = 'update_form.html'
    success_url = '/myprofile/'

    def form_valid(self, form):
        self.object = form.save()
        return super(EditView,self).form_valid(form)

models.py

from django.db import models
from django.contrib.auth.models import AbstractUser

##################################################

class MysiteUser(AbstractUser):
    avatar = models.ImageField(upload_to="avatar")

    def __str__(self):
        return self.username

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