Dropdown plotly from uploaded file

I’m trying to make a dropdown with dash.plot (plotly) from an uploaded file, I already have the code to import the file as csv and excel, and I used the last example of https://dash.plot.ly/getting-started-part-2 to update the dropdown through the columns of the dataframe.
1ºI make a call to load the dropdown options
2º I visualize them, and then I pass them to the callback of the graph. But when I go to the web I don’t get any answer.

import base64
import io
import dash
from dash.dependencies import Input, Output, State
import dash_core_components as dcc
import dash_html_components as html
import dash_table
import pandas as pd

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']

app = dash.Dash(__name__, external_stylesheets=external_stylesheets)

app.config.suppress_callback_exceptions = True

app.layout = html.Div([
            'Drag and Drop or ',
            html.A('Select Files')
            'width': '100%', 'height': '60px', 'lineHeight': '60px',
            'borderWidth': '1px', 'borderStyle': 'dashed',
            'borderRadius': '5px', 'textAlign': 'center', 'margin': '10px'
                 placeholder='Selección de variables'),

def parse_contents(contents, filename):
    content_type, content_string = contents.split(',')
    decoded = base64.b64decode(content_string)
    if 'csv' in filename:
        # Suponga que el usuario ha subido un archivo CSV.
        return pd.read_csv(io.StringIO(decoded.decode('utf-8')))
    elif 'xls' in filename:
        # Suponga que el usuario subido un fichero excel.
        return pd.read_excel(io.BytesIO(decoded))

@app.callback(Output('datatable-upload-container', 'data'),
              [Input('datatable-upload', 'contents')],
              [State('datatable-upload', 'filename')])

def update_output(contents, filename):
    if contents is None:
        return [{''}]
    df = parse_contents(contents, filename)
    return df.to_dict('records')

    Output('datatable-upload-dropdown', 'options'),
    [Input('datatable-upload-container', 'data')])
def set_options(options):
    df = pd.DataFrame(options)
    return [{'label': i, 'value': i} for i in df(options)]

    Output('dropdown-values', 'value'),
    [Input('datatable-upload-dropdown', 'options')])
def set_cities_value(available_options):
    return available_options[0]['value']

@app.callback(Output('datatable-upload-graph', 'figure'),
              [Input('dropdown-values', 'value')]) 

def display_graph(rows):
    df = pd.DataFrame(rows)
    return {
        'value': [{
            'x': df[df.columns[0]],
            'y': df[df.columns[1]],
            'type': 'bar'

if __name__ == '__main__':