Sets this parameter's value on all contexts.

def set_data(self, data):
        """Sets this parameter's value on all contexts."""
        self.shape = data.shape

        if self._data is None:
            assert self._deferred_init, \
                "Parameter '%s' has not been initialized"%self.name
            self._deferred_init = self._deferred_init[:3] + (data,)
            return

        # if update_on_kvstore, we need to make sure the copy stored in kvstore is in sync
        if self._trainer and self._trainer._kv_initialized and self._trainer._update_on_kvstore:
            if self not in self._trainer._params_to_init:
                self._trainer._reset_kvstore()

        for arr in self._check_and_get(self._data, list):
            arr[:] = data