protected final String getCallingConvention() {
		String callingConvention = (String) callingConventionComboBox.getSelectedItem();
		if (callingConvention != null) {
			callingConvention = callingConvention.trim();
		}
		if (callingConvention.length() == 0 ||
			Function.UNKNOWN_CALLING_CONVENTION_STRING.equals(callingConvention)) {
			callingConvention = null;
		}
		return callingConvention;
	}
@return current calling convention selection from dialog.  Null will be returned
if unknown is selected.
Ghidra/Features/Base/src/main/java/ghidra/app/plugin/core/function/AbstractEditFunctionSignatureDialog.java