code: def DEFAULT_NULLVALUE(test):
      
      return False if isinstance(test,bool) \
             else 0 if isinstance(test,int) \
             else 0.0 if isinstance(test,float) \
             else ''
docs: Returns a null value for each of various kinds of test values.
  
      **Parameters**
  
              **test** :  bool, int, float or string
  
                      Value to test.
  
  
      **Returns**
              **null** :  element in `[False, 0, 0.0, '']`
  
                      Null value corresponding to the given test value:
  
                      *   if `test` is a `bool`, return `False`
                      *   else if `test` is an `int`, return `0`
                      *   else if `test` is a `float`, return `0.0`
                      *   else `test` is a `str`, return `''`