def add(self, watch_key, tensor_value):
    """Add a tensor value.

    Args:
      watch_key: A string representing the debugger tensor watch, e.g.,
        'Dense_1/BiasAdd:0:DebugIdentity'.
      tensor_value: The value of the tensor as a numpy.ndarray.
    """
    if watch_key not in self._tensor_data:
      self._tensor_data[watch_key] = _WatchStore(
          watch_key,
          mem_bytes_limit=self._watch_mem_bytes_limit)
    self._tensor_data[watch_key].add(tensor_value)