copy method Null safety

Implementation

SemanticsConfiguration copy() {
  return SemanticsConfiguration()
    .._isSemanticBoundary = _isSemanticBoundary
    ..explicitChildNodes = explicitChildNodes
    ..isBlockingSemanticsOfPreviouslyPaintedNodes = isBlockingSemanticsOfPreviouslyPaintedNodes
    .._hasBeenAnnotated = _hasBeenAnnotated
    .._isMergingSemanticsOfDescendants = _isMergingSemanticsOfDescendants
    .._textDirection = _textDirection
    .._sortKey = _sortKey
    .._attributedLabel = _attributedLabel
    .._attributedIncreasedValue = _attributedIncreasedValue
    .._attributedValue = _attributedValue
    .._attributedDecreasedValue = _attributedDecreasedValue
    .._attributedHint = _attributedHint
    .._hintOverrides = _hintOverrides
    .._tooltip = _tooltip
    .._elevation = _elevation
    .._thickness = _thickness
    .._flags = _flags
    .._tagsForChildren = _tagsForChildren
    .._textSelection = _textSelection
    .._scrollPosition = _scrollPosition
    .._scrollExtentMax = _scrollExtentMax
    .._scrollExtentMin = _scrollExtentMin
    .._actionsAsBits = _actionsAsBits
    .._indexInParent = indexInParent
    .._scrollIndex = _scrollIndex
    .._scrollChildCount = _scrollChildCount
    .._platformViewId = _platformViewId
    .._maxValueLength = _maxValueLength
    .._currentValueLength = _currentValueLength
    .._actions.addAll(_actions)
    .._customSemanticsActions.addAll(_customSemanticsActions);
}