Showing key error at the backend of django when I am receiving data

Question

I want to record audio and send that audio blob to django backend to do some processing. I am using recorder.js for the recording part but it is showing key error while retrieving that blob

I am using xmlhttprequest to send that blob but it is not working

Javascript Code:

var upload = document.createElement('a');
    upload.href="show/";
    upload.innerHTML = "Upload";
    upload.addEventListener("click", function(event){
          var xhr=new XMLHttpRequest();
          xhr.onload=function(e) {
              if(this.readyState === 4) {
                  console.log("Server returned: ",e.target.responseText);
              }
          };
          var fd=new FormData();
          var csrftoken = Cookies.get('csrftoken');
          fd.append("audio_data",blob, filename);
          xhr.open("POST","/show/",true);
          xhr.setRequestHeader("X-CSRFToken", csrftoken);
          xhr.send(fd);
    })

urls.py :

urlpatterns = [
    path('admin/', admin.site.urls),
    path('',views.getmain),
    path('show/',views.solve)
]

views.py"

def solve(request):

    print("post post")
    file = request.FILES['audio_data']
    print(file.size)


    return render(request,'display.html')