I am trying to create a time series plot using Dash in Google Colab however I am getting the below error:

TypeError: ‘NoneType’ object cannot be interpreted as an integer

My code is below:

df['date'] = pd.to_datetime(df['date'], format='%Y-%m-%d')
df['year'] = df['date'].dt.year
sales = df['sales']

app = JupyterDash(__name__)

app.layout = html.Div([
    html.H4('Sales Over Time'),
    dcc.Graph(id='time-series-chart'),
    html.P('Select Year'),
    dcc.Dropdown(
        id='year',
        options=[{'label': year, 'value': year} for year in df['year'].unique()],
        value=df['year'].min(),
        clearable=False
    )
    ])

@app.callback(
    Output('time-series-chart', 'figure'),
    Input('year', 'value')
    )

def update_line_chart(year):
  filtered_df = df[df['year'] == year]
  fig = px.line(filtered_df, x='sales', y=year)
  return fig

app.run_server(mode='inline')

It is meant to give users a drop down where they can select the year and once select produce a graph that shows sales of all sales within that year. your text