[Bug] erro ao usar @register.filter

Estou querendo deixar o numero de telefone mais apresentável, fui usar @register.filter e nao consigo usar load na pagina html

views.py

from django import template
register = template.Library()

@register.filter(name='phone_format')
def phone_format(telephone):
    clear_number = re.sub ('[^0-9]','"',(telephone))
    formatted_number = re.sub((r'(\d{2})(\d{4,5}(\d{4})',r'(\1)\2-\3', clear_number))
    return formatted_number

contatos.html

{% extends 'base.html' %}


{%block conteudo%}



    <h1 class="mt-5">Clientes</h1>

    {% include 'includes/search_bar.html' %}

    <a href="{% url 'dashboard' %}"><button type="button" class="btn btn-outline-secondary">Add Cliente</button></a>


    <table class="table table-striped">
      <thead class="thead-dark">
        <tr>
          <th>ID</th>
          <th>Nome</th>
          <th>Sobrenome</th>
          <th>Telefone</th>
          <th>Aniversário</th>
          <th>Categoria</th>
        </tr>
      </thead>
      <tbody>


        {% for contato in contatos %}
        {% load telephone %}
          <tr>
            <td>{{ contato.id }}</td>
            <td>
              <a href="{% url 'ver_contato' contato.id %}">{{ contato.name }}</a>
            </td>
            <td>{{ contato.surname }}</td>
            <td>{{ telefone.telephone|telephone }}</td>
            <td>{{ contato.birthday }}</td>
            <td>{{ contato.categoria }}</td>
          </tr>
        {% endfor %}



      </tbody>
    </table>

<nav aria-label="Page navigation example">
  <ul class="pagination">
    {% for pagina in contatos.paginator.page_range %}
      {% if contatos.number == pagina %}
        <li class="page-item active">
          <a class="page-link" href="?p={{ pagina }}&termo={{ request.GET.termo }}">{{pagina}}</a>
        </li>
      {% else %}
        <li class="page-item">
          <a class="page-link" href="?p={{ pagina }}&termo={{ request.GET.termo }}">{{pagina}}</a>
        </li>
      {% endif %}
    {% endfor %}
  </ul>
</nav>

{%endblock%}

TemplateSyntaxError at /contatos/ 'telephone' is not a registered tag library. Must be one of: 30 {% load telephone %}

ja mudei todos nomes possiveis do load e continua dando erro nele