code: def head(self, n=10, by=None, **kwargs):
          
          col, id_col = self._query_helper(by=by)
  
          select = ("SELECT %s FROM %s ORDER BY %s ASC LIMIT %d" %
                    (col, self.table.name, id_col, n))
  
          return self._db.query(select, **kwargs)
docs: Get the first n entries for a given Table/Column. Additional keywords
          passed to QueryDb.query().
  
          Requires that the given table has a primary key specified.