removal of dpath -- ready for review (#680)

* first draft for removal of dpath

Signed-off-by: dafnapension <dafnashein@yahoo.com>

* simpler home-made dpath

Signed-off-by: dafnapension <dafnashein@yahoo.com>

* some fixes

Signed-off-by: dafnapension <dafnashein@yahoo.com>

* start code coverage

Signed-off-by: dafnapension <dafnashein@yahoo.com>

* extend code coverage

Signed-off-by: dafnapension <dafnashein@yahoo.com>

* allow spaces in instance keys

Signed-off-by: dafnapension <dafnashein@yahoo.com>

* remove dpath from requirement and expand code coverage

Signed-off-by: dafnapension <dafnashein@yahoo.com>

* cover a few lines of code more

Signed-off-by: dafnapension <dafnashein@yahoo.com>

* cover some more lines of code

Signed-off-by: dafnapension <dafnashein@yahoo.com>

* EncodeLabel is back to instance rather than field operator.

Signed-off-by: dafnapension <dafnashein@yahoo.com>

* live with set_multiple, and avoid premature end of recursive scan

Signed-off-by: dafnapension <dafnashein@yahoo.com>

* cover some more

Signed-off-by: dafnapension <dafnashein@yahoo.com>

* cover more yet again

Signed-off-by: dafnapension <dafnashein@yahoo.com>

---------

Signed-off-by: dafnapension <dafnashein@yahoo.com>

requirements/base.rqr

@@ -2,6 +2,5 @@ datasets>=2.16.0
 evaluate
 mecab-python3
 absl-py
-dpath
 ipadic
 scipy

requirements/docs.rqr

@@ -8,6 +8,5 @@ sacrebleu
 absl-py
 rouge_score
 scikit-learn
-dpath
 jiwer
 editdistance