Sqgturb generate produces exactly n_steps now, not n_steps+1, in order to match other generators

Author: kysolvik

tests/data_sqgturb_test.py

@@ -40,5 +40,5 @@ def test_variable_sizes(sqgturb):
     traj = sqgturb.generate(n_steps=n_steps)
 
     assert traj.system_dim == 18432
-    assert traj.sizes['time'] == n_steps+1
-    assert traj.dab.flatten().shape == (n_steps+1, 18432)
+    assert traj.sizes['time'] == n_steps
+    assert traj.dab.flatten().shape == (n_steps, 18432)