operator [] method Null safety

dynamic operator [](
  1. String key
)

Gets the value of key.

Implementation

operator [](String key) {
  dynamic value = _estimatedData[key];
  if (value is LCRelation) {
    // 反序列化后的 Relation 字段并不完善
    value.key = key;
    value.parent = this;
  }
  return value;
}