@Override
	public void clearSelectedComponents() throws UsrException {
		if (!isClearAllowed()) {
			throw new UsrException("Clearing is not allowed.");
		}
		// If we are on the selection then clear all selected.
		if (this.getNumSelectedComponentRows() <= 0) {
			throw new UsrException("Only selections can be cleared.");
		}
		clearComponents(getSelectedComponentRows());
	}
Returns an attribute value for the cell at <I>columnIndex</I>
and <I>rowIndex</I>.

@param	rowIndex	the row whose value is to be looked up
@param	columnIndex 	the column whose value is to be looked up
@return	the value Object at the specified cell
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/compositeeditor/StructureEditorModel.java