versions/master/api/cpp/docs/api/inherit_graph_40.dot

digraph "Graphical Class Hierarchy"
{
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  edge [fontname="Helvetica",fontsize="10",labelfontname="Helvetica",labelfontsize="10"];
  node [fontname="Helvetica",fontsize="10",shape=record];
  rankdir="LR";
  Node0 [label="dmlc::nullopt_t",height=0.2,width=0.4,color="black", fillcolor="white", style="filled",URL="$structdmlc_1_1nullopt__t.html",tooltip="dummy type for assign null to optional"];
}