old_contents: from sqlite3 import Connection, Row
  
  
  class Decoder:
      def __init__(self):
          self.conn = Connection('nes.sqlite')
          self.conn.row_factory = Row
  
      def __del__(self):
          self.conn.close()
  
      def decode(self, opcode):
          c = self.conn.cursor()
          c.execute('select * from instruction where opcode=?', [opcode])
          row = c.fetchone()
          return dict(zip(row.keys(), row))
  
new_contents: from sqlite3 import Connection, Row
  
  
  class Decoder:
      def __init__(self):
          self.conn = Connection('nes.sqlite')
          self.conn.row_factory = Row
  
      def __del__(self):
          self.conn.close()
  
      def decode(self, opcode):
          c = self.conn.cursor()
          c.execute('select * from instruction where opcode=?', [opcode])
          row = c.fetchone()
          if row:
              return dict(zip(row.keys(), row))
          else:
              raise NotImplementedError('Undocumented Opcode: ' + str(opcode))
  
subject: Raise an exception when it's an undocumented opcode.