/usr/share/doc/libtruffle-java/api/com/oracle/nfi/ is in libtruffle-java-doc 0.6-2.
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/usr/share/doc/libtruffle-java/api/com/oracle/nfi/NativeFunctionInterfaceRuntime.html
/usr/share/doc/libtruffle-java/api/com/oracle/nfi/api/
/usr/share/doc/libtruffle-java/api/com/oracle/nfi/api/NativeFunctionHandle.html
/usr/share/doc/libtruffle-java/api/com/oracle/nfi/api/NativeFunctionInterface.html
/usr/share/doc/libtruffle-java/api/com/oracle/nfi/api/NativeFunctionPointer.html
/usr/share/doc/libtruffle-java/api/com/oracle/nfi/api/NativeLibraryHandle.html
/usr/share/doc/libtruffle-java/api/com/oracle/nfi/api/package-frame.html
/usr/share/doc/libtruffle-java/api/com/oracle/nfi/api/package-summary.html
/usr/share/doc/libtruffle-java/api/com/oracle/nfi/api/package-tree.html
/usr/share/doc/libtruffle-java/api/com/oracle/nfi/package-frame.html
/usr/share/doc/libtruffle-java/api/com/oracle/nfi/package-summary.html
/usr/share/doc/libtruffle-java/api/com/oracle/nfi/package-tree.html