My FirebaseFirestore looks like the below image

My code snipped for deserialization is as below:

class StripeProductPlan extends Equatable {
  final DocumentReference selfRef;

  final Map<String, String> metaData;
  final String name;
  final String? role;
  final String? taxCode;

  const StripeProductPlan({
    required this.selfRef,
    required this.metaData,
    required this.name,
    this.role,
    this.taxCode,
  });

 factory StripeProductPlan.fromSnapshot(
      DocumentSnapshot<Map<String, dynamic>> snapshot) {
    final data = snapshot.data()!;
    return StripeProductPlan(
      metaData: data['metaData'] as Map<String, String>,
      selfRef: snapshot.reference,
      name: data['name'] as String,
      role: data['role'] as String? ?? '',
      taxCode: data['taxCode'] as String? ?? '',
    );
  }

Everything else works, except for the metaData deserialization. How do I fix this?