addBinding(binding) {
    if (!binding) {
      return;
    }

    const bindings = this.bindings.get(binding.scope);
    const existingBinding = bindings.get(binding.identifier.name);

    if (existingBinding && existingBinding !== binding) {
      throw new Error(
        `scopeTracker.addBinding: ` +
          `Binding "${existingBinding.identifier.name}" already exists. ` +
          `Trying to add "${binding.identifier.name}" again.`
      );
    }

    bindings.set(binding.identifier.name, binding);
  }
Add a binding to Tracker in binding's own Scope
@param {Binding} binding