columnar::ColumnAccessorOptions Node1 columnar::ColumnAccessor Options + isOptional + addMTDependency + makeColumnInfo() Node2 std::string     Node2->Node1 +replacesColumn Node3 std::basic_string< Char >     Node3->Node2 Node4 std::vector< std::string > + elements + elements   Node4->Node1 +internalLinkTargetNames