docs: function extractJsdoc(comment) {
      var docAst = doctrine.parse(comment, { unwrap: true, sloppy: true });
      if (!docAst.tags || docAst.tags.length === 0) {
          return null;
      }
      // only interested in @param @property, and @return
      var paramTags = docAst.tags.filter(function(tag) {
          return tag.title === "param";
      }).map(jsdocTagToFlowTag);
  
      var returnTags = docAst.tags.filter(function(tag) {
          return tag.title === "return" || tag.title === "returns";
      }).map(jsdocTagToFlowTag);
  
      var propTags = docAst.tags.filter(function(tag) {
          return tag.title === "property" || tag.title === "prop";
      }).map(jsdocTagToFlowTag);
  
      return {
          params: paramTags,
          returns: returnTags,
          props: propTags
      };
  }