testbook.ref cannot recognize complex variable

[HypocriticalLemur]

It appears, that testbook passes string instead of complex variable when testing a function that takes a complex number as an argument.
I attached three files.
Complex.ipynb contains function 'func_complex' that takes one complex argument.
complex_testbook.ipynb is a test file. It contains one of your simple references. It tries to call func_complex.
Please add complex type to the testbook (see the patch attached)

testbook_complex.zip