Exporting/serialization html.Div to Json

Hi! I have trouble with serialization html.div as a json. I want to export page (where is assigned html.div) to json and save it. Then I want to regenerate page with the same html. Method to_plotly_json generates bad json:
{‘namespace’: ‘dash_html_components’, ‘type’: ‘Div’, ‘props’: {‘children’: [H1(children=‘This’, role=‘a role’), H2(‘is’), H3(‘a page’), Textarea(value=‘Textarea1’), Div([H4(‘Div with textarea!’)])]}}

(lack of ’ ’ after 'props;). Could someone help me?

class Tab():
def __init__(self,name):
    self.name= name
    self.page = html.Div(
        [
            html.H1('This',role="a role"),
            html.H2('is'),
            html.H3('a page'),
            dcc.Textarea(value='Textarea1'),
            html.Div([html.H4('Div with textarea!')])

        ]
    )


def dumpJson(self):
    el_list=str(self.page.to_plotly_json())
    f = open(env.json_save_path,"w")
    f.write(el_list)
    f.close()