'prefix is prepended to the prefix of the member forms
Keyword arguments are:
key=form_class, key2=form_class2, ...
The form_class can be a Form, a Formset, or a MultiForm.
It is currently not possible to specify ctor arguments to the form_class.'

def __init__(self, prefix='', **kwargs):

    self._form_types = kwargs
    self._is_bound = False
    self._prefix = prefix
