/usr/include/shogun/kernel/string/ is in libshogun-dev 3.2.0-7.3build4.
This file is owned by root:root, with mode 0o755.
..
/usr/include/shogun/kernel/string/CommUlongStringKernel.h
/usr/include/shogun/kernel/string/CommWordStringKernel.h
/usr/include/shogun/kernel/string/DistantSegmentsKernel.h
/usr/include/shogun/kernel/string/FixedDegreeStringKernel.h
/usr/include/shogun/kernel/string/GaussianMatchStringKernel.h
/usr/include/shogun/kernel/string/HistogramWordStringKernel.h
/usr/include/shogun/kernel/string/LinearStringKernel.h
/usr/include/shogun/kernel/string/LocalAlignmentStringKernel.h
/usr/include/shogun/kernel/string/LocalityImprovedStringKernel.h
/usr/include/shogun/kernel/string/MatchWordStringKernel.h
/usr/include/shogun/kernel/string/OligoStringKernel.h
/usr/include/shogun/kernel/string/PolyMatchStringKernel.h
/usr/include/shogun/kernel/string/PolyMatchWordStringKernel.h
/usr/include/shogun/kernel/string/RegulatoryModulesStringKernel.h
/usr/include/shogun/kernel/string/SNPStringKernel.h
/usr/include/shogun/kernel/string/SalzbergWordStringKernel.h
/usr/include/shogun/kernel/string/SimpleLocalityImprovedStringKernel.h
/usr/include/shogun/kernel/string/SparseSpatialSampleStringKernel.h
/usr/include/shogun/kernel/string/SpectrumMismatchRBFKernel.h
/usr/include/shogun/kernel/string/SpectrumRBFKernel.h
/usr/include/shogun/kernel/string/StringKernel.h
/usr/include/shogun/kernel/string/StringSubsequenceKernel.h
/usr/include/shogun/kernel/string/WeightedCommWordStringKernel.h
/usr/include/shogun/kernel/string/WeightedDegreePositionStringKernel.h
/usr/include/shogun/kernel/string/WeightedDegreeStringKernel.h