def allowed_push_targets_field(parent_key):
    if parent_key:
        help_text = 'Allowed push targets (subset from parent %s)' % parent_key
    else:
        help_text = 'Allowed push targets'

    return serializers.SlugRelatedField(
        many=True,
        slug_field='name',
        queryset=PushTarget.objects.all(),
        default=[],
        help_text=help_text) 

def _get_field_type(serializer, field_name, field, include_read_only):
    """
    Try to describe a field type.
    """
    if not include_read_only and hasattr(field, 'writable_doc_format'):
        return _get_type_from_docstring(field.writable_doc_format)

    if hasattr(field, 'doc_format'):
        return _get_type_from_docstring(field.doc_format)

    if isinstance(field, (relations.ManyRelatedField, serializers.ListSerializer)):
        # Many field, recurse on child and make it a list
        if isinstance(field, relations.ManyRelatedField):
            field = field.child_relation
        else:
            field = field.child
        return [_get_field_type(serializer, field_name, field, include_read_only)]

    if field.__class__.__name__ in _SERIALIZER_DEFS:
        return _SERIALIZER_DEFS[field.__class__.__name__]

    if isinstance(field, serializers.SlugRelatedField):
        return _get_details_for_slug(serializer, field_name, field)

    if isinstance(field, serializers.SerializerMethodField):
        # For method fields try to use docstring of the method.
        method_name = field.method_name or 'get_{field_name}'.format(field_name=field_name)
        method = getattr(serializer, method_name, None)
        if method:
            docstring = getattr(method, '__doc__')
            return _get_type_from_docstring(docstring, docstring or 'method')

    if isinstance(field, serializers.BaseSerializer):
        return describe_serializer(field, include_read_only)

    logger = logging.getLogger(__name__)
    logger.error('Undocumented field %s' % field)
    return 'UNKNOWN'