Removed warning for Widget.is_hidden property.

import copy

from itertools import chain

import warnings

from django.conf import settings

from django.forms.utils import flatatt, to_current_timezone

from django.utils.datastructures import MultiValueDict, MergeDict

from django.utils.deprecation import RemovedInDjango18Warning

from django.utils.encoding import force_text, python_2_unicode_compatible

from django.utils.html import conditional_escape, format_html

from django.utils.translation import ugettext_lazy

    def is_hidden(self):

        return self.input_type == 'hidden' if hasattr(self, 'input_type') else False

    @is_hidden.setter

    def is_hidden(self, *args):

        warnings.warn(

            "`is_hidden` property is now read-only (and checks `input_type`). "

            "Please update your code.",

            RemovedInDjango18Warning, stacklevel=2

        )

    def subwidgets(self, name, value, attrs=None, choices=()):

        """

        Yields all "subwidgets" of this widget. Used only by RadioSelect to