Adapt docstring

Author: SabineHaas

windpowerlib/density.py

@@ -31,6 +31,7 @@ def barometric(pressure, pressure_height, hub_height, temperature_hub_height):
     -------
     pandas.Series or numpy.array
         Density of air at hub height in kg/m³.
+        Returns a pd.Series if one of the input parameters is a pd.Series.
 
     Notes
     -----
@@ -87,6 +88,7 @@ def ideal_gas(pressure, pressure_height, hub_height, temperature_hub_height):
     -------
     pandas.Series or numpy.array
         Density of air at hub height in kg/m³.
+        Returns a pd.Series if one of the input parameters is a pd.Series.
 
     Notes
     -----