If hicn-light deb package does not include the API file an external plugin  needs to checkout the entire source code. 

For instance the hicn-light sysrepo plugin needs it.

root@9199ff2e7305:/opt/hicn/utils/sysrepo-plugins/build# cmake .. -DSR_PLUGINS_DIR=/usr/lib/x86_64-linux-gnu/sysrepo/plugins
/usr/lib/x86_64-linux-gnu/libvapiclient.so
– Could NOT find PkgConfig (missing: PKG_CONFIG_EXECUTABLE)
– Could NOT find PkgConfig (missing: PKG_CONFIG_EXECUTABLE)
– Could NOT find Hicnlight (missing: HICNLIGHT_LIBRARIES HICNLIGHT_INCLUDE_DIRS)
Build number is: b1
CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
/opt/hicn/utils/sysrepo-plugins/hicn-light/HICNLIGHT_INCLUDE_DIR
used as include directory in directory /opt/hicn/utils/sysrepo-plugins/hicn-light
/opt/hicn/utils/sysrepo-plugins/hicn-plugin/VAPI_INCLUDE_DIR
used as include directory in directory /opt/hicn/utils/sysrepo-plugins/hicn-plugin
/opt/hicn/utils/sysrepo-plugins/hicn-plugin/VLIB_API_INCLUDE_DIR
used as include directory in directory /opt/hicn/utils/sysrepo-plugins/hicn-plugin
/opt/hicn/utils/sysrepo-plugins/hicn-plugin/VNET_INCLUDE_DIR
used as include directory in directory /opt/hicn/utils/sysrepo-plugins/hicn-plugin
/opt/hicn/utils/sysrepo-plugins/hicn-plugin/VPP_ALL_INCLUDE_DIR
used as include directory in directory /opt/hicn/utils/sysrepo-plugins/hicn-plugin
/opt/hicn/utils/sysrepo-plugins/hicn-plugin/VPP_MSG_INCLUDE_DIR
used as include directory in directory /opt/hicn/utils/sysrepo-plugins/hicn-plugin
HICNLIGHT_LIBRARY (ADVANCED)
linked by target "hicnlight" in directory /opt/hicn/utils/sysrepo-plugins/hicn-light