TypeError : expected bytes-like object, not HttpResponse

i am trying to send an email with pdf file attached. But I have an error when sending the email in my project django

utils.py

from io import BytesIO
from django.http import HttpResponse
from django.template.loader import get_template

from xhtml2pdf import pisa

def render_to_pdf(template_src, context_dict={}):
  template = get_template(template_src)
  html  = template.render(context_dict)
  result = BytesIO()
  pdf = pisa.pisaDocument(BytesIO(html.encode("UTF-8")), result)
  if not pdf.err:
    return HttpResponse(result.getvalue(),
    content_type='application/pdf')
    return None

views.py

def sendMail(request):
    ""
    pdf = render_to_pdf('cart/commande.html',context)
    subject, from_email, to = 'Message with pièce joint : N° 0001', 
    'aab@gmail.com', 
    'too@gmail.com'
    text_content = 'hello'
    html_content = '<p>hello, .</p>'
    msg = EmailMultiAlternatives(subject, text_content, from_email, [to])
    msg.attach_alternative(html_content, "text/html")
    msg.attach('commande_pdf',pdf,'application/pdf')
    msg.send()
    return render(request,'cart/succes.html')

the error points to this line msg.send

Noted the generation of the pdf file is OK, it must be attached to the email

return result.getvalue()