Legend makes it associated with the subplot with dynamically responsive design and the ability to enable turn off individual trace

The current legend_tracegroupgap implementation is in pixel.

Desired behavior:
if I have 2 subplots (col=2, row=1) to be able to enable legend_per_subplot = True

Default vertical legend on the right side:
subplot(2 traces) | Legend with 2 traces
subplot(4 traces) | Legend with 4 traces

The workaround with legend_tracegroupgap does not match the need as they are expressed in pixels instead of domain-like subplots.

首先检查当前的 legend_tracegroupgap 实现，以及 Python 绘图库中图例与子图的关联方式。当一个两列一行的子图布局能够启用每个子图的图例、每个图例只显示其关联子图中的 traces，并采用响应式定位而不是基于像素的间距时，这项工作就完成了。