! \internal Disassociates \a el from this layout. This is done by setting the \ref QCPLayoutElement::layout and the \ref QCPLayerable::parentLayerable to zero. The QObject parent is set to the parent QCustomPlot. This method is used by subclass specific methods that remove elements from the layout (e.g. \ref take or \ref takeAt). Note that this method only changes properties in \a
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