为什么在分层布局中使用子图时，这个边不直？

Question

下面的 MWE 生成了一个简单的图。当我将两个上部节点 A1 和 B1 添加到子图中时，水平对齐会丢失，这是可以理解的，因为子图中的节点独立于其他节点定位。我不明白的是，从 B1 到 B3 的连接不再是直线了。我该如何在保留子图的同时修复这个问题？

注意：我需要在更复杂的示例中使用子图，在那里我会遇到同样的问题。

\documentclass[border=0.125cm]{standalone}
\usepackage{tikz}
\usetikzlibrary{graphdrawing}
\usetikzlibrary{graphs,quotes} 
\usegdlibrary{trees,layered,force}
\begin{document} 
\tikz \graph[layered layout] { 
    "A1";
    "B1";    
    "B3";
    "A2";
    "A3";
    "C";  
    "A2" -- "A3";
    "A3" -- "C";
    "B1" --[minimum layers=2] "B3";
    "A1" -- "A2";
    "B3" -- "C";
};
\tikz \graph[layered layout] { 
//[layered layout]{
    "A1";
    "B1";
    };
    "B3";
    "A2";
    "A3";
    "C";     
    "A2" -- "A3";
    "A3" -- "C";
    "B1" --[minimum layers=2] "B3";
    "A1" -- "A2";
    "B3" -- "C";
};
\end{document}

Answer 1

后期的解决方法：bend left=0针对该边或所有边设置：

%! TEX program = lualatex
\RequirePackage{luatex85}
\documentclass[border=0.125cm]{standalone}
\usepackage{tikz}
\usetikzlibrary{graphdrawing}
\usetikzlibrary{graphs,quotes} 
\usegdlibrary{trees,layered,force}
\begin{document} 
\tikz \graph[layered layout] { 
    "A1";
    "B1";    
    "B3";
    "A2";
    "A3";
    "C";  
    "A2" -- "A3";
    "A3" -- "C";
    "B1" --[minimum layers=2] "B3";
    "A1" -- "A2";
    "B3" -- "C";
};
\tikz \graph[layered layout,edges={bend left=0}] { 
//[layered layout]{
    "A1";
    "B1";
    };
    "B3";
    "A2";
    "A3";
    "C";     
    "A2" -- "A3";
    "A3" -- "C";
    "B1" --[minimum layers=2, bend left=0] "B3";
    "A1" -- "A2";
    "B3" -- "C";
};
\end{document}