Bip32KeyData constructor
      
      Bip32KeyData({ 
    
    
- Bip32Depth? depth,
 - Bip32KeyIndex? index,
 - Bip32ChainCode? chainCode,
 - Bip32FingerPrint? parentFingerPrint,
 
Implementation
Bip32KeyData({
  Bip32Depth? depth,
  Bip32KeyIndex? index,
  Bip32ChainCode? chainCode,
  Bip32FingerPrint? parentFingerPrint,
})  : depth = depth ?? Bip32Depth(0),
      index = index ?? Bip32KeyIndex(0),
      chainCode = chainCode ?? Bip32ChainCode(),
      parentFingerPrint = parentFingerPrint ?? Bip32FingerPrint();