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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def edit_form(self, obj=None):
 """Edit form."""

        kbtype = request.args['kbtype'] if 'kbtype' in request.args else 'w'

        if kbtype == KnwKB.KNWKB_TYPES['written_as']:
            self.form = WrittenAsKnowledgeForm
        elif kbtype == KnwKB.KNWKB_TYPES['dynamic']:
            self.form = DynamicKnowledgeForm
        else:
            self.form = TaxonomyKnowledgeForm

        form = self.form(obj=obj)

        if not form.is_submitted():
            # load extra data: obj => form
            if kbtype == KnwKB.KNWKB_TYPES['dynamic']:
                if obj.kbdefs:
                    form.id_collection.data = obj.kbdefs.id_collection
                    form.output_tag.data = obj.kbdefs.output_tag
                    form.search_expression.data = obj.kbdefs.search_expression

            if kbtype == KnwKB.KNWKB_TYPES['taxonomy']:
                file_name = obj.get_filename()
                if os.path.isfile(file_name):
                    form.tfile.label.text = form.tfile.label.text + " *"
                    # TODO add the possibility to download the file
                    form.tfile.description = _("Already uploaded %(name)s",
                                               name=obj.get_filename())

        form.kbtype.data = kbtype

        return form