bebop_teleop: Cannot locate rosdep definition for [libsdl2-ttf-dev]

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hello all ! I want to use a package bebop_teleop but it is dependent on libsdl2-ttf-dev. As I already installed libsdl2-ttf-dev but when I type in terminal

rosdep install bebop_teleop

so I get an error that

bebop_teleop: Cannot locate rosdep definition for [libsdl2-ttf-dev]

When I try to install libsdl2-ttf-dev using the command

sudo apt-get install libsdl2-dev

I get the following message which shows that its already installed.

0 upgraded, 0 newly installed, 0 to remove and 88 not upgraded.

Please help me to solve this problem, thanks all.