LeapMotionFrame "is_valid" attribute not found.

Hello, I am attempting to determine whether a leap Frame is valid or not so that I am not continuously sending 0 to all the joints if the user's hand is out of view of the controller. I have added a method isFrameValid into LeapMotion.java. This is on the master branch by the way. Here is the Leap Documentation on the subject https://developer-archive.leapmotion.com/documentation/v2/python/api/Leap.Frame.html

  public boolean isFrameValid() {
    return controller.frame().is_valid;

This refuses to compile and attempting to extract this information via my test script below doesn't seem to work either.

     [echo] compile start
    [javac] Compiling 989 source files to /run/media/nick/c9aafeb5-ec91-4d34-959a-05b1c1d6f0c8/MRL_MASTER/myrobotlab/build/classes
    [javac] /run/media/nick/c9aafeb5-ec91-4d34-959a-05b1c1d6f0c8/MRL_MASTER/myrobotlab/src/org/myrobotlab/service/LeapMotion.java:66: error: cannot find symbol
    [javac]     return controller.frame().is_valid;
    [javac]                              ^
    [javac]   symbol:   variable is_valid
    [javac]   location: class Frame
    [javac] Note: Some input files use or override a deprecated API.
    [javac] Note: Recompile with -Xlint:deprecation for details.
    [javac] Note: Some input files use unchecked or unsafe operations.
    [javac] Note: Recompile with -Xlint:unchecked for details.
    [javac] 1 error

/run/media/nick/c9aafeb5-ec91-4d34-959a-05b1c1d6f0c8/MRL_MASTER/myrobotlab/build.xml:704: Compile failed; see the compiler error output for details.