sort_xtable(a_xlist2d, key_index)
Sort each XList in two dimensional XList according to the order of the sub XList of the specified index.
A two dimensional XList means an XList instance of which all elements are XList instances.
Parameters
- (list of lists) : a XList instance of to sort each XList instance in it.
- key_index (integer) : An index of a XList instance which determine the sorting order.
Result
list of lists :A sorted two deimensional XList instance. The returned XList instance is identical to the XList instance passed as an argument.