Question insv- class copy method

package test_pkg; 

  typedef enum bit {rd, wr} typ_dir; 
  typedef logic [15:0] typ_data; 
  typedef logic [15:0] typ_addr; 
  
  typedef class stream; 

class packet; 
   static int next_ID; 
   const int ID; 

  rand typ_data data; 
   rand typ_addr addr; 
   rand typ_dir dir; 

  function new(); 
    ID = next_ID++; 
  endfunction 

  function packet copy(); 
    packet clone; 
     clone.dir  = dir; 
     clone.addr = addr; 
     clone.data = data; 
     return clone; 
  endfunction 
  
  function bit compare(packet other); 
    if (other.dir !== dir) return 0; 
    if (other.addr !== addr) return 0; 
    if (other.data !== data) return 0; 
   return 1; 
  endfunction 
  
  function string psprint(); 
    string kind; 
    kind = (dir==rd) ? "Read" : "Write";; 
    $sformat (psprint, "%s packet %0d:  a=%h, D=%h...id=%h",kind,data,addr,dir,ID ); 
  endfunction 
    
endclass 

class stream; 
  string name; 
   packet history [$]; 

  function packet get_trans(bit print = 1'b0); 
    packet t; 
     t = new(); 
     void'(t.randomize()); 
     history.push_back(t); 
    if (print) 
      $display ("Stream %s generated %s\n", name, t.psprint()); 
     return t; 
   endfunction : get_trans 
    
  function new(string name = "default"); 
    this.name = name; 
  endfunction 
    
  endclass 

endpackage 

module top; 

  import test_pkg::*; 

  stream one = new (); 

  packet t, t1, t2; 

  initial begin 

    
  repeat (10) 
   begin 
      t = one.get_trans(1); 
      #1000; 
      $display ("%t.....",$time); 
   end 
    for (int i=0; i<one.history.size(); i++) 
      $display( "%d: %s", i, one.history[i].psprint() ); 

    t = one.get_trans(); 
    t1 = t.one.copy();          
    t2 = one.get_trans(); 
  end 

endmodule

virtual function packet clone();
  clone = new();
  clone.copy(this);
endfunction
function void copy(packet rhs);
     this.dir  = rhs.dir; 
     this.addr = rhs.addr; 
     this.data = rhs.data; 
endfunction

class packet2 extends packet;
int id;
virtual function packet2 clone();
  clone = new();
  clone.copy(this);
endfunction
function void copy(packet rhs);
     super.copy(rhs); // copies everything in the base class
     this.id= rhs.id; // copy the extended properties. 
endfunction 
endclass