Django olwidget MultiInfoLayer

from collections import Iterable

from django import forms
from django.conf import settings
from django.template.loader import render_to_string
from django.utils import simplejson
from django.utils.encoding import smart_str
from django.utils.safestring import mark_safe

from olwidget import utils
from olwidget.widgets import InfoLayer

class MultiInfoLayer(InfoLayer):
    def _prepare_single_layer(self, layer):
        wkt_array = []
        for geom, attr in layer:
            wkt = utils.get_ewkt(geom)
            if isinstance(attr, dict):
                wkt_array.append( [wkt, utils.translate_options(attr)] )
            else:
                wkt_array.append( [wkt, attr] )
        return wkt_array

    def prepare(self, name, value, attrs=None):
        wkt_array = []
        if isinstance( self.info[0], Iterable ):
            for layer in self.info:
                wkt_array += self._prepare_single_layer( layer )
        else:
            wkt_array += self._prepare_single_layer( self.info )
        info_json = simplejson.dumps(wkt_array)

        if name and not self.options.has_key('name'):
            self.options['name'] = forms.forms.pretty_name(name)

        context = {
            'info_array': info_json,
            'options': simplejson.dumps(utils.translate_options(self.options)),
            'STATIC_URL': settings.STATIC_URL,
        }
        context.update(self.get_extra_context())
        js = mark_safe(render_to_string(self.template, context))
        html = ""
        return (js, html)