fix docstrings in background.py
@@ -98,12 +98,13 @@ class Background3D(BackgroundIRF):
>>> print(bkg_3d)
Background3D
------------
-
+ <BLANKLINE>
axes : ['energy', 'fov_lon', 'fov_lat']
shape : (21, 36, 36)
ndim : 3
unit : 1 / (MeV s sr)
dtype : >f4
+ <BLANKLINE>
"""
tag = "bkg_3d"
