Inconsistent row and col parameters used to add vline to faceted subplots

I'm trying to have a vertical line added to faceted plots, with the line being at a different position for every subplot. Here's a MRE:

import plotly.express as px
import pandas as pd
import numpy as np
from itertools import product

# Prepare data
combinations = list(product(range(1, 11), repeat=2))
df = pd.DataFrame(combinations, columns=['cat', 'x'])
df['y'] = np.random.randint(1, 100, size=len(df))

# Figure
fig = px.line(df, x='x', y='y', facet_col='cat', facet_col_wrap=3)

# Add vlines in a loop
def generate_lines(n, d):
    tuples_list = []
    a = 1  # Initial value for a
    b = 1  # Initial value for b
    for i in range(1, n+1):
        tuples_list.append((i, a, b))
        if i % d == 0:  # Check if the divider is reached
            a += 1  # Increment a when the divider is reached
            b = 1   # Reset b to 1 when the divider is reached
        else:
            b += 1  # Increment b otherwise
    return tuples_list

lines = generate_lines(10, 3)
for i, a, b in lines:
    fig.add_vline(x=i, row=a, col=b, opacity=1, line_width=2, line_dash='dash', line_color='red')

fig.show()

What this code should produce is a vertical line at the value of the cat parameter but this is obviously not the case:

It took me a while to figure out what's actually happening. The issue is that the row argument does not start at the top left in the same way as faceting does, but instead starts at the bottom left. As a result, the (1,2) plot with a value of 2 is not shown because that's an empty space (would correspond to cat=11) and the 2nd subplot does not receive their vertical line.

This leads to inconsistencies and the required code to make the location more complicated because e.g. reducing the number of categories to 9 would mean that (1,1) needs to suddenly get a value of 7.

The behavior would be more intuitive if row 1 was the top one instead of the bottom one. If this is not a bug but a feature, it would be good to have this explicitly stated in the documentation / API reference.

Using plotly 5.13.0

Empieza reproduciendo el MRE proporcionado con plotly 5.13.0, centrándote en cómo facet_col_wrap asigna las filas de los subplots y en cómo add_vline interpreta row y col. Inspecciona el comportamiento de los facets y de las filas/columnas de los subplots expuesto por estas APIs. Se considera terminado cuando la numeración de las filas coincide con el diseño de faceting o cuando la documentación/referencia de la API explica claramente el comportamiento existente y su workaround.