First on the code, this is a c + + primer the above case,

 ostream& Print (ostream & amp; OS, const QueryResult & amp; Qr) {
OS & lt; //print each word 
For (auto m: * qr. Lines) {
OS & lt; <"(line" & lt; } 
Return the OS; 
} 

The qr. Lines are STD: : from & lt; STD: : set Call this smart pointer type, set the size of object () function, display an error

As shown in figure

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