Optional Output Custom Python Block

Hello everyone,

Using gnuradio3.8 on Mac.

I'm trying to write a custom python block (not an embedded python block) with an optional output.  I have the "optional" flag set to true in the YAML file, so GRC doesn't complain when it isn't connected.  The block is working fine when the second port is connected, but if it isn't it complains:

insufficient connected output ports (2 needed, 1 connected)

It's an interp block with vector i/o--don't know if that makes a difference.  The constructor looks like this:

gr.interp_block.__init__(self,

name="optional_output",

in_sig=[(np.float32, self.vlen)],

out_sig=[(np.float32, self.vlen),

(np.float32, self.vlen)],

interp=self.interp_rate)

Thank you,

Cameron