How to use the @chainsafe/ssz-type-schema.UintImpl.bigint function in @chainsafe/ssz-type-schema

export function _defaultValue(type: FullSSZType): any {
  switch (type.type) {
    case Type.bool:
      return false;
    case Type.uint:
      switch (type.use) {
        case UintImpl.bn:
          return new BN(0);
        case UintImpl.bigint:
          return BigInt(0);
        case UintImpl.number:
          return 0;
      }
      break;
    case Type.bitList:
      return BitList.fromBitfield(Buffer.alloc(0), 0);
    case Type.bitVector:
      return BitVector.fromBitfield(
        Buffer.alloc(Math.max(1, Math.ceil(type.length / 8))),
        type.length);
    case Type.byteList:
      return Buffer.alloc(0);
    case Type.byteVector:
      return Buffer.alloc(type.length);
    case Type.list: