docs: update copy

Author: kgryte

src/array_api_stubs/_draft/linear_algebra_functions.py

@@ -27,13 +27,15 @@ def matmul(x1: array, x2: array, /) -> array:
     Returns
     -------
     out: array
-        -   if both ``x1`` and ``x2`` are one-dimensional arrays having shape ``(N,)``, a zero-dimensional array containing the inner product as its only element.
-        -   if ``x1`` is a two-dimensional array having shape ``(M, K)`` and ``x2`` is a two-dimensional array having shape ``(K, N)``, a two-dimensional array containing the `conventional matrix product <https://en.wikipedia.org/wiki/Matrix_multiplication>`_ and having shape ``(M, N)``.
-        -   if ``x1`` is a one-dimensional array having shape ``(K,)`` and ``x2`` is an array having shape ``(..., K, N)``, an array having shape ``(..., N)`` (i.e., prepended dimensions during vector-to-matrix promotion **must** be removed) and containing the `conventional matrix product <https://en.wikipedia.org/wiki/Matrix_multiplication>`_.
-        -   if ``x1`` is an array having shape ``(..., M, K)`` and ``x2`` is a one-dimensional array having shape ``(K,)``, an array having shape ``(..., M)`` (i.e., appended dimensions during vector-to-matrix promotion **must** be removed) and containing the `conventional matrix product <https://en.wikipedia.org/wiki/Matrix_multiplication>`_.
-        -   if ``x1`` is a two-dimensional array having shape ``(M, K)`` and ``x2`` is an array having shape ``(..., K, N)``, an array having shape ``(..., M, N)`` and containing the `conventional matrix product <https://en.wikipedia.org/wiki/Matrix_multiplication>`_ for each stacked matrix.
-        -   if ``x1`` is an array having shape ``(..., M, K)`` and ``x2`` is a two-dimensional array having shape ``(K, N)``, an array having shape ``(..., M, N)`` and containing the `conventional matrix product <https://en.wikipedia.org/wiki/Matrix_multiplication>`_ for each stacked matrix.
-        -   if either ``x1`` or ``x2`` has more than two dimensions, an array having a shape determined by :ref:`broadcasting` ``shape(x1)[:-2]`` against ``shape(x2)[:-2]`` and containing the `conventional matrix product <https://en.wikipedia.org/wiki/Matrix_multiplication>`_ for each stacked matrix.
+        output array.
+
+        -   If both ``x1`` and ``x2`` are one-dimensional arrays having shape ``(N,)``, the returned array **must** be a zero-dimensional array and **must** contain the inner product as its only element.
+        -   If ``x1`` is a two-dimensional array having shape ``(M, K)`` and ``x2`` is a two-dimensional array having shape ``(K, N)``, the returned array **must** be a two-dimensional array and **must** contain the `conventional matrix product <https://en.wikipedia.org/wiki/Matrix_multiplication>`_ and having shape ``(M, N)``.
+        -   If ``x1`` is a one-dimensional array having shape ``(K,)`` and ``x2`` is an array having shape ``(..., K, N)``, the returned array **must** be an array having shape ``(..., N)`` (i.e., prepended dimensions during vector-to-matrix promotion **must** be removed) and **must** contain the `conventional matrix product <https://en.wikipedia.org/wiki/Matrix_multiplication>`_.
+        -   If ``x1`` is an array having shape ``(..., M, K)`` and ``x2`` is a one-dimensional array having shape ``(K,)``, the returned array **must** be an array having shape ``(..., M)`` (i.e., appended dimensions during vector-to-matrix promotion **must** be removed) and **must** contain the `conventional matrix product <https://en.wikipedia.org/wiki/Matrix_multiplication>`_.
+        -   If ``x1`` is a two-dimensional array having shape ``(M, K)`` and ``x2`` is an array having shape ``(..., K, N)``, the returned array **must** be an array having shape ``(..., M, N)`` and **must** contain the `conventional matrix product <https://en.wikipedia.org/wiki/Matrix_multiplication>`_ for each stacked matrix.
+        -   If ``x1`` is an array having shape ``(..., M, K)`` and ``x2`` is a two-dimensional array having shape ``(K, N)``, the returned array **must** be an array having shape ``(..., M, N)`` and **must** contain the `conventional matrix product <https://en.wikipedia.org/wiki/Matrix_multiplication>`_ for each stacked matrix.
+        -   If either ``x1`` or ``x2`` has more than two dimensions, the returned array **must** be an array having a shape determined by :ref:`broadcasting` ``shape(x1)[:-2]`` against ``shape(x2)[:-2]`` and **must** contain the `conventional matrix product <https://en.wikipedia.org/wiki/Matrix_multiplication>`_ for each stacked matrix.
 
         The returned array **must** have a data type determined by :ref:`type-promotion`.