old_contents: 
  // Originally from https://github.com/draft-js-utils/draft-js-utils/blob/master/src/Constants.js.
  export const BLOCK_TYPE = {
      // This is used to represent a normal text block (paragraph).
      UNSTYLED: 'unstyled',
      HEADER_ONE: 'header-one',
      HEADER_TWO: 'header-two',
      HEADER_THREE: 'header-three',
      HEADER_FOUR: 'header-four',
      HEADER_FIVE: 'header-five',
      HEADER_SIX: 'header-six',
      UNORDERED_LIST_ITEM: 'unordered-list-item',
      ORDERED_LIST_ITEM: 'ordered-list-item',
      BLOCKQUOTE: 'blockquote',
      PULLQUOTE: 'pullquote',
      CODE: 'code-block',
      ATOMIC: 'atomic',
      // HR block.
      BREAK: 'atomic:break',
  };
  
  // Originally from https://github.com/draft-js-utils/draft-js-utils/blob/master/src/Constants.js.
  export const ENTITY_TYPE = {
      LINK: 'LINK',
      DOCUMENT: 'DOCUMENT',
      MODEL: 'MODEL',
      IMAGE: 'IMAGE',
      EMBED: 'EMBED',
      HORIZONTAL_RULE: 'HORIZONTAL_RULE',
  };
  
  // Originally from https://github.com/draft-js-utils/draft-js-utils/blob/master/src/Constants.js.
  export const INLINE_STYLE = {
      BOLD: 'BOLD',
      CODE: 'CODE',
      ITALIC: 'ITALIC',
      STRIKETHROUGH: 'STRIKETHROUGH',
      UNDERLINE: 'UNDERLINE',
  };
  
new_contents: 
  // Originally from https://github.com/draft-js-utils/draft-js-utils/blob/master/src/Constants.js.
  export const BLOCK_TYPE = {
      // This is used to represent a normal text block (paragraph).
      UNSTYLED: 'unstyled',
      HEADER_ONE: 'header-one',
      HEADER_TWO: 'header-two',
      HEADER_THREE: 'header-three',
      HEADER_FOUR: 'header-four',
      HEADER_FIVE: 'header-five',
      HEADER_SIX: 'header-six',
      UNORDERED_LIST_ITEM: 'unordered-list-item',
      ORDERED_LIST_ITEM: 'ordered-list-item',
      BLOCKQUOTE: 'blockquote',
      CODE: 'code-block',
      ATOMIC: 'atomic',
  };
  
  // Originally from https://github.com/draft-js-utils/draft-js-utils/blob/master/src/Constants.js.
  export const ENTITY_TYPE = {
      LINK: 'LINK',
      DOCUMENT: 'DOCUMENT',
      MODEL: 'MODEL',
      IMAGE: 'IMAGE',
      EMBED: 'EMBED',
      HORIZONTAL_RULE: 'HORIZONTAL_RULE',
  };
  
  // Originally from https://github.com/draft-js-utils/draft-js-utils/blob/master/src/Constants.js.
  export const INLINE_STYLE = {
      BOLD: 'BOLD',
      CODE: 'CODE',
      ITALIC: 'ITALIC',
      STRIKETHROUGH: 'STRIKETHROUGH',
      UNDERLINE: 'UNDERLINE',
  };
  
subject: Remove deprecated/unused block types