Sets and returns the handler name for the command as a String. The handler specifies the name of
the function or subroutine that implements the command. In other
words, the Handler is the name of the callback function that
Softimage calls each time the command is invoked.
Note: It is possible to implement a simple script-based command
without a handler. Such a command cannot have any arguments and
Softimage will execute the code at the global scope of script
rather than calling a subroutine.
For commands implemented with the C++ API this property is not
necessary because the handler is always OnXSICommandCPP(). For more
information see the Custom Commands chapter of the SDK
Customization guide.