[WIP] Fix 170 - an improved patch

[GiggleLiu]

This is fix the issue in comment: #170 (comment)

But there are still some bugs related to Zygote.

e.g.

julia> Zygote.gradient(x->x.content.theta, Daggered(Rx(0.5)))
(nothing,)

I do not know why this gradient is so hard for Zygote. @Roger-luo

[codecov]

Codecov Report

Merging #173 (438d4dc) into master (f3fede2) will decrease coverage by 0.03%.
The diff coverage is 82.14%.

@@            Coverage Diff             @@
##           master     #173      +/-   ##
==========================================
- Coverage   81.13%   81.09%   -0.04%     
==========================================
  Files          46       46              
  Lines        2136     2185      +49     
==========================================
+ Hits         1733     1772      +39     
- Misses        403      413      +10     

Impacted Files	Coverage Δ
src/autodiff/chainrules_patch.jl	87.50% <82.14%> (-8.25%)	⬇️

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