size method
Returns the serialized byte length of input.
Implementation
@override
int size(final Map<String, dynamic> input) {
  assertLength(schema.length, input.length);
  int size = 0;
  for (final MapEntry<String, BorshCodec> entry in schema.entries) {
    final dynamic value = input[entry.key];
    size += entry.value.size(value);
  }
  return size;
}