Add docstring to PsVecHorizontal

src/pystencils/backend/ast/vector.py

@@ -41,7 +41,16 @@ class PsVecBroadcast(PsUnOp, PsVectorOp):
 
 
 class PsVecHorizontal(PsBinOp, PsVectorOp):
-    """Extracts scalar value from N vector lanes."""
+    """Represents a binary operation between a scalar and a vector operand.
+    With the binary operation not being vectorized, a horizontal reduction
+    along the lanes of the vector operand is required to extract a scalar value.
+    The result type will be equal to the scalar operand.
+
+    Args:
+        scalar_operand: Scalar operand
+        vector_operand: Vector operand to be converted to a scalar value
+        reduction_op: Binary operation that is also used for the horizontal reduction
+    """
 
     __match_args__ = ("lanes", "scalar_operand", "vector_operand", "reduction_op")