}

  return std::nullopt;
}

void SetXlaInternalScope(Node* node, StringPiece scope) {
  node->AddAttr(kXlaInternalScopeAttr, scope);
}

// NB! We append a new scope as suffix to the _XlaInternalScope attribute
// instead of overriding the old value.  In other words, appending scope B to
// scope A creates the conjunction of the scopes A and B (i.e, A & B) and,

  // Look for either _XlaScope or _XlaInternalScope on both nodes to guide
  // clustering.  If both nodes have a scope and the scopes do not match, do
  // not cluster along this edge.  If even one of the nodes lacks a scope
  // attribute, then it is treated as a "bridge" and a cluster may be created
  // along it.
  //
  // The difference between _XlaScope and _XlaInternalScope is that _XlaScope is