code: @Override
      public long getLong(@NonNull String key) {
          if (key == null) { throw new IllegalArgumentException("key cannot be null."); }
  
          synchronized (lock) {
              return CBLConverter.asLong(getMValue(internalDict, key), internalDict);
          }
      }
docs: Gets a property's value as an long.
  Floating point values will be rounded. The value `true` is returned as 1, `false` as 0.
  Returns 0 if the value doesn't exist or does not have a numeric value.
  
  @param key the key
  @return the long value.