YAML is a markup language with many powerful features
YAML uses a fixed indentation scheme to represent relationships between data layers.
Each level consists of exactly two spaces. DO NOT USE TABS.
key value pair using colon.
list of items
For existing files, You can convert tabs to 2 spaces by these commands in Vim::set tabstop=2 expandtab and then :retab.
The suggested syntax for YAML files is to use 2 spaces for indentation,