@Override
  public boolean setResult(T value, boolean isLast, Map<String, Object> extras) {
    return super.setResult(Preconditions.checkNotNull(value), isLast, extras);
  }
Sets the result to {@code value}.

<p>This method will return {@code true} if the value was successfully set, or {@code false} if
the data source has already been set, failed or closed.

<p>If the value was successfully set and {@code isLast} is {@code true}, state of the data
source will be set to {@link AbstractDataSource.DataSourceStatus#SUCCESS}.

<p>This will also notify the subscribers if the value was successfully set.

@param value the value to be set
@param isLast whether or not the value is last.
@return true if the value was successfully set.
fbcore/src/main/java/com/facebook/datasource/SimpleDataSource.java