human
Solve the following python programming problem given the following code:
def get_validator(self, data_field_class) : 
    '
        Returns a validator to be used in bulk import
        ' 
    def validate_choices(field, value) : 
        if (field.choices and value and (unicode (value) not in field.choices)) : 
            return _ ("'{value}' is not a valid choice for {slug}, the available options are: {options}.").format (value = value, slug = field.slug, options = ', '.join (field.choices)) 
def validate_required(field, value) : 
        if (field.is_required and (not value)) : 
            return _ ('Cannot create or update a {entity} without the required field: {field}.').format (entity = data_field_class.entity_string, field = field.slug) 
def validate_custom_fields(custom_fields) : 
        errors = [] 
        for field in self.fields : 
            value = custom_fields.get (field.slug, None) 
            errors.append (validate_required (field, value)) 
            errors.append (validate_choices (field, value)) 
return ' '.join (filter (None, errors)) 
return validate_required 

    
    

    Fix the buggy line: return validate_required
assistant
#Here is Python code to fix the buggy line: return validate_required
.

return def validate_custom_fields(