code: def unset(*args, **kw):
      
  
      if len(kw) != 0:
          raise SyntaxError("unset requires a list of variable names")
  
      for arg in args:
          if arg in _varDict:
              del _varDict[arg]
docs: Unset IRAF environment variables.
  
      This is not a standard IRAF task, but it is obviously useful.  It makes the
      resulting variables undefined.  It silently ignores variables that are not
      defined.  It does not change the os environment variables.