def __call__(cls, *args, **kwargs):
    """
        Construct a new `Form` instance.

        Creates the `_unbound_fields` list and the internal `_wtforms_meta`
        subclass of the class Meta in order to allow a proper inheritance
        hierarchy.
        """
    if cls._unbound_fields is None:
        fields = []
        for name in dir(cls):
            if not name.startswith('_'):
                unbound_field = getattr(cls, name)
                if hasattr(unbound_field, '_formfield'):
                    fields.append((name, unbound_field))
        fields.sort(key=lambda x: (x[1].creation_counter, x[0]))
        cls._unbound_fields = fields
    if cls._wtforms_meta is None:
        bases = []
        for mro_class in cls.__mro__:
            if 'Meta' in mro_class.__dict__:
                bases.append(mro_class.Meta)
        cls._wtforms_meta = type('Meta', tuple(bases), {})
    return type.__call__(cls, *args, **kwargs)
