'Return cleaned data, including additional requested fields.'

def clean(self):

    cleaned_data = super(BlockListGetForm, self).clean()
    additional_requested_fields = ['student_view_data', 'block_counts', 'nav_depth', 'block_types_filter']
    for additional_field in additional_requested_fields:
        field_value = cleaned_data.get(additional_field)
        if (field_value or (field_value == 0)):
            cleaned_data['requested_fields'].add(additional_field)
    usage_key = cleaned_data.get('usage_key')
    if (not usage_key):
        return
    cleaned_data['user'] = self._clean_requested_user(cleaned_data, usage_key.course_key)
    return cleaned_data
