code: function decorateWithReadConcern(command, coll) {
    let readConcern = Object.assign({}, command.readConcern || {});
    if (coll.s.readConcern) {
      Object.assign(readConcern, coll.s.readConcern);
    }
  
    if (Object.keys(readConcern).length > 0) {
      Object.assign(command, { readConcern: readConcern });
    }
  }
docs: Applies a read concern to a given command.
  
  @param {object} command the command on which to apply the read concern
  @param {Collection} coll the parent collection of the operation calling this method