foo.rb

AllowedTypes = %i[query commit].to_set
private def assert_valid_tx_type(tx_type)
  unless valid_tx_type?(tx_type)
    raise ArgumentError, "tx_type must be one of the following: #{AllowedTypes.inspect[1..-2]}"
  end
end

private def valid_tx_type?(tx_type)                                                        
  AllowedTypes.include?(tx_type)
end