[FEAT] Add root_output property to access root octree levels

Author: Leguark

gempy_engine/core/data/solutions.py

@@ -63,6 +63,13 @@ def block_solution_resolution(self) -> np.ndarray:
                 raise ValueError("Block solution type not recognized.")
 
         return resolution
+    
+    @property
+    def root_output(self) -> OctreeLevel:
+        """Get the root output where you can find all the grids other than the octree grid, and lvl0 of the octree."""
+        if not self.octrees_output:
+            raise ValueError("No octree levels available.")
+        return self.octrees_output[0]
 
     @property
     def raw_arrays(self) -> RawArraysSolution: