anchor.diff:  * `!`: Not
   * Range operator `(-)` : a value such as `"3-5"` means a value between 3 to 5 (inclusive). This is only supported in the following attributes
   ** `replica`
  +** array operator . e.g: `sysprop.zone = ["east", "west","apac"]`. This is equivalent to having multiple rules with each of these values. This can be used in the following attributes
  +** `sysprop.*`
  +** `port`
  +** `ip_*`
  +** `node`
  +** `diskType`
   * None means equal
   
   ==== Special functions
  
positive.code: 
  For the above rule to work, all nodes must the started with a system property called `"zone"`
  
  
  ==== Place Replicas Based on Node Role
  Do not place any replica on a node which has the overseer role. Note that the role is added by the `addRole` collection API. It is *not* automatically the node which is currently the overseer.
  
negative.code: [source,json]
  {"replica": "#ALL", "freedisk": ">500"}
  
  Keep all replicas in nodes with over `50%` freedisk
  [source,json]
  {"replica": "#ALL", "freedisk": ">50%"}
  
  