clean method for bulk edit method is not getting called

**Model**
`file_item = models.FileField(blank=False, verbose_name=_('ABC'),)`

**Admin**
```

def ModelAdmin():
action = ['bulk_edit_action']
bulk_list_display = ['file_item']
form = FileFieldForm

def FileFieldForm(RalphAdminForm):
file_item = forms.FileField()
def clean_file_item():
# do some stuff
```

**Expected behaviour**
Want this file field clean method to be called