Utensil

From https://github.com/pygae/galgebra/pull/149#issuecomment-564450759 : > If you do, `from sympy import diff` it'll use the sympy function regardless of the environment variable value. If you do `from sympy.core.backend import diff`, then...

| python-3.7 | python-3.7-sympy-1.5 | python-3.7-symengine | |------------|------------------------|------------------------| | 3m 47s | 4m 56s | 3m 55s | The time is weird. Why is sympy-1.5 slower?

Now it fails at https://app.circleci.com/jobs/github/pygae/galgebra/944/tests with 4 erros: - `TypeError: no default __reduce__ due to non-trivial __cinit__` - `TypeError: __new__() takes exactly 3 positional arguments (2 given)` - `AttributeError: 'Mul'...

> There are more errors than that, they're just hidden under "more" Scrolled to the very bottom, I don't see the "more"? 

> Ah, you're using the new GUI which has no "more" button any longer. Have you found any more error types?

We need a more efficient way to "uniq" and filter errors.

> Somewhat related: [symengine/symengine.py#302](https://github.com/symengine/symengine.py/issues/302) Seems not the same issue. We could easily work around this or fix it at https://github.com/symengine/symengine.py/blob/master/symengine/lib/symengine_wrapper.pyx#L1589-L1593 like https://github.com/symengine/symengine.py/blob/master/symengine/lib/symengine_wrapper.pyx#L1786 GitHubsymengine/symengine.pyPython wrappers for SymEngine. Contribute to symengine/symengine.py development...

It looks good to me except the name could be something without a "and" and more general, like `ExtendableProperty` and class method is optional and we could integrate cached_property together...

`involution` should be implemented. See also my implementation at https://github.com/pygae/GAlgebra.jl/blob/874dd59844fee98b918d070d6265353dcd3c1547/src/mv.jl#L243 . GitHubpygae/GAlgebra.jlJulia interface to GAlgebra via PyCall. Contribute to pygae/GAlgebra.jl development by creating an account on GitHub.

Yeah indeed.