/usr/include/dlib/graph/ is in libdlib-dev 18.18-1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/dlib/graph/graph_kernel_1.h
/usr/include/dlib/graph/graph_kernel_abstract.h
/usr/include/dlib/graph_cuts/find_max_factor_graph_potts.h
/usr/include/dlib/graph_cuts/find_max_factor_graph_potts_abstract.h
/usr/include/dlib/graph_cuts/general_flow_graph.h
/usr/include/dlib/graph_cuts/general_potts_problem.h
/usr/include/dlib/graph_cuts/graph_labeler.h
/usr/include/dlib/graph_cuts/graph_labeler_abstract.h
/usr/include/dlib/graph_cuts/min_cut.h
/usr/include/dlib/graph_cuts/min_cut_abstract.h
/usr/include/dlib/graph_utils/edge_list_graphs.h
/usr/include/dlib/graph_utils/edge_list_graphs_abstract.h
/usr/include/dlib/graph_utils/find_k_nearest_neighbors_lsh.h
/usr/include/dlib/graph_utils/find_k_nearest_neighbors_lsh_abstract.h
/usr/include/dlib/graph_utils/function_objects.h
/usr/include/dlib/graph_utils/function_objects_abstract.h
/usr/include/dlib/graph_utils/graph_utils.h
/usr/include/dlib/graph_utils/graph_utils_abstract.h
/usr/include/dlib/graph_utils/ordered_sample_pair.h
/usr/include/dlib/graph_utils/ordered_sample_pair_abstract.h
/usr/include/dlib/graph_utils/sample_pair.h
/usr/include/dlib/graph_utils/sample_pair_abstract.h