Embedded Python Block - Variable Input Vector

I created an embedded python block (using version 3.9 from git) successfully but I need the input vector to be variable size based on the parameters. For example:

in_sig=[(np.byte, a*b)],

out_sig=[(np.byte, a*b)]

However, the parameters have defaults and defaults appear to set the vector. I can't change the preceding stream to vector block or else the grc has an error, but when I run the grc there is an input error because I was not able to update the steam to vector block. A block that does this similarly is a Reed Solomon block whose yml file is:

https://github.com/gnuradio/gnuradio/blob/master/gr-dtv/grc/dtv_dvbt_reed_solomon_enc.block.yml

However as far as I can tell there is no way to add a yml file for an embedded python block so I tried to create a python OOT module. However I must be making a mistake because when I go to build the block I error with:

make[2]: *** No rule to make target '../python/bindings/gnuradio-test', needed by 'python/bindings/extracted_docstrings.json'.  Stop.
make[1]: *** [CMakeFiles/Makefile2:377: python/bindings/CMakeFiles/extracted_docstrings.dir/all] Error 2
make: *** [Makefile:141: all] Error 2

I think I need to do something from this guide: https://wiki.gnuradio.org/index.php/GNU_Radio_3.9_OOT_Module_Porting_Guide

but I haven't figured out the right process. Can anyone help steer me in the right direction?

Thanks,

Tim