def push_only?
      chunks.each do |c|
        return false if !c.opcode.nil? && c.opcode > OP_16
      end
      true
    end
def push_only?
      chunks.each do |c|
        return false if !c.opcode.nil? && c.opcode > OP_16
      end
      true
    end
whether data push only script which dose not include other opcode