ex 2.92 - extract-term same var case

simply tests passsed
ex 2.92 - slight mod on tests
ex 2.92 - rename var -> target-var
ex 2.92 - extract-term - first full impl
ex 2.92 - cannot mix poly with diff var now
ex 2.92 - planning auto-var-conversion
ex 2.92 - auto variable wrapping
ex 2.92 - extract impl done
ex 2.92 - try fetch all variables from a poly
ex 2.92 - more complex example on fetch-var
ex 2.92 - extract-order - remove duplicate members
ex 2.92 - sort symbols
ex 2.92 - remove unused output
ex 2.92 - do-extraction, naive impl
ex 2.92 - some correction (not working ...)
ex 2.92 - debuging

still not working, I guess it's a tag related issue but
that's all today.
ex 2.92 - weird double poly-tag
ex 2.92 - poly - do-extract works
ex 2.92 - show examples
ex 2.92 - extract-all -> all in one step