Plot Matplotlib shades of red where there are missing values in time series

Question

How do I plot vertical rectangles or highlights that show the missing data areas on this matplotlib time series plot? After importing both matplotlib and pandas, I can generate this image below, but the highlights of missing date intervals are not showing up.

def plot_missing(main):
    m_df = fill_missing_timestamps(main[['Date', 'Mean']], 'Mean')

    # Find missing 'Mean' values
    missing_values = m_df['Mean'].isna()

    # Create a mask for missing data
    mask = np.zeros_like(m_df['Mean'])
    mask[missing_values] = 1

    # Identify the start and end indices of missing data intervals
    start_indices = np.where(np.diff(mask) == 1)[0] + 1
    end_indices = np.where(np.diff(mask) == -1)[0]

    # Check if the first or last data point is missing
    if missing_values.iloc[0]:
        start_indices = np.insert(start_indices, 0, 0)
    if missing_values.iloc[-1]:
        end_indices = np.append(end_indices, len(main) - 1)

    # Create a separate column for the missing data intervals
    interval_column = np.zeros_like(m_df['Mean'])
    for start, end in zip(start_indices, end_indices):
        interval_column[start:end+1] = 1

    # Plot the time series with missing data in red and non-missing data in blue
    plt.plot(m_df['Date'], m_df['Mean'], color='pink', label='Non-Missing Data')
    plt.scatter(m_df['Date'][interval_column == 1], m_df['Mean'][interval_column == 1],
                color='red', label='Missing Data')

    # Set the title and labels
    plt.title('Raw Data \n Missing Data', fontweight='bold', fontsize=18)
    plt.xlabel('Date')
    plt.ylabel('Mean')
    plt.legend()

    plt.show()
    return

plot_missing(main)

Thank you