add complex fill value decoding

[xzackli]

Complex arrays can end up specifying a fill value of Any[0.0, 0.0], which needs to be converted into the appropriate complex number.

[asinghvi17]

Thanks, could you add a test for this?

[meggart]

I agree, a small test, ideally one that includes some python interoperability would be highly appreciated

[lazarusA]

bump