code: function _getPreviousSiblingThatIsNotBlank(node) {
      var previousSibling = node.previousSibling;
      while (previousSibling && _isBlankTextNode(previousSibling)) {
        previousSibling = previousSibling.previousSibling;
      }
      return previousSibling;
    }
docs: Returns previous sibling node that is not a blank text node