The following Python code..
import codac as cdc
from scipy.linalg import sqrtm
..generates the warning:
UserWarning: Signature b'\x99\x99\x99\x99\x99\x99\xb9\xbf' for <class 'numpy.float64'> does not match any known type: falling back to type probe function.
(from @godardma: quick fix, import Codac after Scipy)