docs: update docstrings

src/psimpy/simulator/mass_point_model.py

@@ -217,14 +217,15 @@ class MassPointModel:
         -------
         output: numpy array
             Time history of the mass point's location and velocity.
-            :code`output.shape[1]` is :math:`6`. More specifically:
-            :code:`output[:,0]` contains the time steps,
-            :code:`output[:,1]` contains the `x` coordinates,
-            :code:`output[:,2]` contains the `y` coordinates,
-            :code:`output[:,3]` contains velocity values in `x` direction,
-            :code:`output[:,4]` contains velocity values in `y` direction,
-            :code:`output[:,5]` contains total velocity values.
-        
+            2d :class:`numpy.ndarray`. Each row corresponds to a time step and
+            each column corresponds to a quantity. In total :math:`6` columns,
+            namely :code:`output.shape[1]=6`. More specifically:
+            :code:`output[:,0]` are the time steps,
+            :code:`output[:,1]` are the `x` coordinates,
+            :code:`output[:,2]` are the `y` coordinates,
+            :code:`output[:,3]` are velocity values in `x` direction,
+            :code:`output[:,4]` are velocity values in `y` direction,
+            :code:`output[:,5]` are total velocity values.
         """
         fgrad_x, fgrad_y, fgrad_xx, fgrad_yy, fgrad_xy = \
             self._preprocess(elevation, x0, y0)