Doc before insert:
  li:{} [root] FIRST li:{empty} LAST li:{non-empty}
   li:{empty} 
   li:{non-empty} FIRST te:{key1} LAST te:{key2}
    te:{key1} {val1}
    te:{key2} {val2}
Node before insert:
  te:{} [root] [nodoc] {"to_be_inserted"}
-
Doc after insert:
  li:{} [root] FIRST te:{} LAST li:{non-empty}
   te:{} {"to_be_inserted"}
   li:{empty} 
   li:{non-empty} FIRST te:{key1} LAST te:{key2}
    te:{key1} {val1}
    te:{key2} {val2}
Node after insert:
  te:{} {"to_be_inserted"}
