DJANGO CookBook - Custom list filter

admin.py

# Tested in Django 1.6

# Import default list filter
from django.contrib.admin import SimpleListFilter

# Create the filter
class InvoicePaidFilter(SimpleListFilter):
    title = _('Paid')
    parameter_name = 'paid'
    
    # Set the displaying options
    def lookups(self, request, model_admin):
        return (
            ('PAID', _('Paid')),
            ('UNPAID', _('Unpaid')),
        )

    # Assign a query for each option
    def queryset(self, request, queryset):
        if self.value() == 'PAID':
            return queryset.filter(paid=True)
        elif self.value() == 'UNPAID':
            return queryset.exclude(paid=True)
            

# Assign the filter
class InvoiceAdmin(admin.ModelAdmin):
    list_filter = [InvoicePaidFilter,]
    ...

How can I display the count of records in front of each filter?
i.e display in list filter
Paid(5),
Unpaid(10)
Thanks