Multiplication of transformations of different degrees is sometimes allowed but shouldn't be


I'm seeing:

~~~
In [1]: from libsemigroups_pybind11 import *

In [2]: x = Transf([0])

In [3]: x
Out[3]: Transf([0])

In [4]: y = Transf([0,0])

In [5]: x * y
Out[5]: Transf([0])

In [6]: y * x
Out[6]: Transf([0, 0])
~~~

would have expected an error for both of these products. 