Update tree.ts

[dholakiyaankit]

Added observable fix

[codecov]

Codecov Report

Merging #329 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #329   +/-   ##
=======================================
  Coverage   92.13%   92.13%           
=======================================
  Files          25       25           
  Lines        1030     1030           
  Branches      146      146           
=======================================
  Hits          949      949           
  Misses         53       53           
  Partials       28       28

Impacted Files	Coverage Δ
src/tree.ts	92.82% <100%> (ø)	⬆️

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