def validate_read_concern_option(read_concern)
      return unless enabled?
      return if read_concern.nil?
      unless read_concern.is_a?(Hash)
        raise Error::LintError, "Read concern is not a hash: #{read_concern}"
      end
      return if read_concern.empty?
      keys = read_concern.keys
      if keys != [:level]
        raise Error::LintError, "Read concern has invalid keys: #{keys.inspect}"
      end
      level = read_concern[:level]
      return if [:local, :majority, :snapshot].include?(level)
      raise Error::LintError, "Read concern level is invalid: #{level.inspect}"
    end
def validate_read_concern_option(read_concern)
      return unless enabled?
      return if read_concern.nil?
      unless read_concern.is_a?(Hash)
        raise Error::LintError, "Read concern is not a hash: #{read_concern}"
      end
      return if read_concern.empty?
      keys = read_concern.keys
      if keys != [:level]
        raise Error::LintError, "Read concern has invalid keys: #{keys.inspect}"
      end
      level = read_concern[:level]
      return if [:local, :majority, :snapshot].include?(level)
      raise Error::LintError, "Read concern level is invalid: #{level.inspect}"
    end
Validates the provided hash as a read concern object, per the
 read/write concern specification
 (https://github.com/mongodb/specifications/blob/master/source/read-write-concern/read-write-concern.rst#read-concern).

 This method also accepts nil as input for convenience.

 The read concern document as sent to the server may include
 additional fields, for example afterClusterTime. These fields
 are generated internally by the driver and cannot be specified by
 the user (and would potentially lead to incorrect behavior if they
 were specified by the user), hence this method prohibits them.

 @param [ Hash ] read_concern The read concern options hash,
   with the following optional keys:
   - *:level* -- the read preference level as a symbol; valid values
      are *:local*, *:majority*, and *:snapshot*

 @raise [ Error::LintError ] If the validation failed.