Polish reader folder error message

[chenwhql]

Required（必填, multiple choices, two at most）

• PR type（PR 类型） is ( F ):
  A. New features（新功能）---------------- D. Performance optimization（性能优化）
  B. Bug fixes（问题修复）------------------ E. Breaking changes（向后不兼容的改变）
  C. Function optimization（功能优化）------F. Others（其它）

• PR changes（改动点）is ( D ):
  A. OPs（operators）---------------------- C. Docs（文档）
  B. APIs（接口）--------------------------- D. Others（其它）

• Use one sentence to describe what this PR does.（简述本次PR的目的和改动）

1. polish error messag in operators/reader folder.
2. add white list for invalid enforce count shell.

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Optional（选填, If None, please delete it）

• Describe what this PR does in detail. If this PR fixes an issue, please give the issue id.

• If you modified docs, please make sure that both Chinese and English docs were modified and provide a preview screenshot. （文档必填）

• Please write down other information you want to tell reviewers.

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