code: def set(self, item, column=None, value=None):
          
          if value is not None:
              self._visual_drag.set(item, ttk.Treeview.column(self, column, 'id'), value)
          return ttk.Treeview.set(self, item, column, value)
docs: Query or set the value of given item.
  
          With one argument, return a dictionary of column/value pairs for the
          specified item. With two arguments, return the current value of the
          specified column. With three arguments, set the value of given column
          in given item to the specified value.
  
          :param item: item's identifier
          :type item: str
          :param column: column's identifier
          :type column: str, int or None
          :param value: new value