code: def initialize(self,  **kwargs):
          
          if not set(kwargs.keys()).issuperset(self.init_keys):
              raise Exception("TransferFn needs to be initialized with %s"
                              % ','.join(repr(el) for el in self.init_keys))
docs: Transfer functions may need additional information before the
          supplied numpy array can be modified in place. For instance,
          transfer functions may have state which needs to be allocated
          in memory with a certain size. In other cases, the transfer
          function may need to know about the coordinate system
          associated with the input data.