// LAMMPS -> Python
digraph api {
    rankdir="LR";
    edge [constraint=false];
    input [shape=box label="LAMMPS\nInput Script" height=1.5];
    subgraph cluster0 {
      style=filled;
      color="#e5e5e5";
      rank=same;
      capi [shape=box style=filled height=1 color="#666666" fontcolor=white label="LAMMPS\nC Library API"];
      instance [shape=box style=filled height=1 color="#3465a4" fontcolor=white label="LAMMPS\ninstance\n\n0x01abcdef"];
      capi -> instance [dir=both];
      label="LAMMPS Shared Library\nor LAMMPS Executable";
    }
    python [shape=box style=filled color="#4e9a06" fontcolor=white label="Python\nScript" height=1.5];
    subgraph cluster1 {
      style=filled;
      color="#e5e5e5";
      lammps [shape=box style=filled height=1 color="#729fcf" label="lammps\n\nptr: 0x01abcdef"];
      label="LAMMPS Python Module";
    }
    input -> instance [constraint=true];
    instance -> python [dir=both constraint=true];
    python:e -> lammps:w [dir=both constraint=true];
    lammps:s -> capi:e [dir=both label=ctypes constraint=true];
}