Importing two items from astro_util in one call was giving cyclic err…

…ors between

black (which added a line between the imports and the docstring below) and
docformatter (which kept removing the line mentioned above). By calling two
separate instances of import slsim.astro_util... I was able to clear the
cyclic error.

slsim/Sources/SourceVariability/variability.py

@@ -2,10 +2,9 @@
     LightCurveInterpolation,
 )
 from slsim.Sources.SourceVariability.sinusoidal_variability import SinusoidalVariability
-from slsim.Util.astro_util import (
-    generate_signal_from_bending_power_law,
-    generate_signal_from_generic_psd,
-)
+from slsim.Util.astro_util import generate_signal_from_bending_power_law
+from slsim.Util.astro_util import generate_signal_from_generic_psd
+
 """This class aims to have realistic variability models for AGN and supernovae."""