[Enesuygurs]

HeatMapWithTime._get_self_bounds() looped over self.data as if it were a flat list of points. But data is a list of time steps, and each step holds a list of [lat, lng(, weight)] points. So point[0] and point[1] were whole points, not coordinates.

As a result:

• get_bounds() returned nested lists such as [[[48.0, 3.0, 0.5], [51.0, 5.0]], ...] instead of [[48.0, 3.0], [52.0, 6.0]].
• With any other layer on the map, Map.get_bounds() raised TypeError: '<' not supported between instances of 'list' and 'float'.
• An empty time step raised IndexError.

This breaks the common m.fit_bounds(m.get_bounds()) pattern for maps with a HeatMapWithTime.

import folium
from folium.plugins import HeatMapWithTime

m = folium.Map()
folium.Marker([50, 4]).add_to(m)
HeatMapWithTime([[[48.0, 3.0], [52.0, 6.0]]]).add_to(m)
m.get_bounds()  # TypeError before this change

The fix iterates over the points in every time step. The new test covers weighted points, an empty time step and a map with another layer. It fails without the change and passes with it.