Multi select input in admin site - django

Question

I am trying to create a form in Admin site that uses two fields from two different tables (Employee, Product) as input (single select & multi-select) and make it available for admin user selection and write this to another table (JobQueue).
Following is my code.
models.py
class Employee(models.Model):
id = models.IntegerField(primary_key=True, verbose_name='Employee Code')
name = models.CharField(max_length=200, verbose_name='Employee Name')
def __str__(self):
return self.name
class Product(models.Model):
STATUS = (('New', 'New'), ('Go', 'Go'), ('Hold', 'Hold'), ('Stop', 'Stop'))
code = models.IntegerField(primary_key=True, max_length=3, verbose_name='Product Code')
name = models.CharField(max_length=100, verbose_name='Product Name')
def __str__(self):
return self.name
class JobQueue(models.Model):
emp_name = models.CharField(max_length=200, default='1001')
product_code = models.CharField(max_length=200, default='100')
admin.py:
class JobQueueAdmin(admin.ModelAdmin):
form = JobQueueForm
fieldsets = (
(None,{'fields': ('emp_name', 'product_code'),}),)
def save_model(self, request, obj, form, change):
super(JobQueueAdmin, self).save_model(request, obj, form, change)
forms.py:
class JobQueueForm(forms.ModelForm):
# Single select drop down
emp_name = forms.ModelChoiceField(queryset=Employee.objects.all(), widget=forms.ChoiceField())
# Multiselect checkbox
product_code = forms.MultiValueField(queryset=Product.objects.all(), widget=forms.CheckboxSelectMultiple(), required=False)
def save(self, commit=True):
return super(JobQueueForm, self).save(commit = commit)
class Meta:
model = JobQueue
fields = ('emp_name', 'product_code')
When I start the web-server, I get the following error:
AttributeError: 'ModelChoiceField' object has no attribute 'to_field_name'
Could someone please help me how do I let the user to pick the values from JobQueueForm and save the same in JobQueue table ?