Update the docstrings of erf functions, because they are also ufuncs

Author: antonwolfy

dpnp/scipy/special/_erf.py

@@ -69,7 +69,7 @@ def __init__(
             mkl_impl_fn=mkl_impl_fn,
         )
 
-    def __call__(self, x, out=None):  # pylint: disable=signature-differs
+    def __call__(self, x, /, out=None):
         return super().__call__(x, out=out)
 
 
@@ -84,8 +84,12 @@ def __call__(self, x, out=None):  # pylint: disable=signature-differs
 ----------
 x : {dpnp.ndarray, usm_ndarray}
     Input array, expected to have a real-valued floating-point data type.
-out : {dpnp.ndarray, usm_ndarray}, optional
+out : {None, dpnp.ndarray, usm_ndarray, tuple of ndarray}, optional
     Optional output array for the function values.
+    A tuple (possible only as a keyword argument) must have length equal to the
+    number of outputs.
+
+    Default: ``None``.
 
 Returns
 -------
@@ -140,8 +144,12 @@ def __call__(self, x, out=None):  # pylint: disable=signature-differs
 ----------
 x : {dpnp.ndarray, usm_ndarray}
     Input array, expected to have a real-valued floating-point data type.
-out : {dpnp.ndarray, usm_ndarray}, optional
+out : {None, dpnp.ndarray, usm_ndarray, tuple of ndarray}, optional
     Optional output array for the function values.
+    A tuple (possible only as a keyword argument) must have length equal to the
+    number of outputs.
+
+    Default: ``None``.
 
 Returns
 -------
@@ -185,8 +193,12 @@ def __call__(self, x, out=None):  # pylint: disable=signature-differs
 ----------
 x : {dpnp.ndarray, usm_ndarray}
     Input array, expected to have a real-valued floating-point data type.
-out : {dpnp.ndarray, usm_ndarray}, optional
+out : {None, dpnp.ndarray, usm_ndarray, tuple of ndarray}, optional
     Optional output array for the function values.
+    A tuple (possible only as a keyword argument) must have length equal to the
+    number of outputs.
+
+    Default: ``None``..
 
 Returns
 -------
@@ -231,8 +243,12 @@ def __call__(self, x, out=None):  # pylint: disable=signature-differs
 x : {dpnp.ndarray, usm_ndarray}
     Input array, expected to have a real-valued floating-point data type.
     Domain: [-1, 1].
-out : {dpnp.ndarray, usm_ndarray}, optional
+out : {None, dpnp.ndarray, usm_ndarray, tuple of ndarray}, optional
     Optional output array for the function values.
+    A tuple (possible only as a keyword argument) must have length equal to the
+    number of outputs.
+
+    Default: ``None``.
 
 Returns
 -------
@@ -284,8 +300,12 @@ def __call__(self, x, out=None):  # pylint: disable=signature-differs
 x : {dpnp.ndarray, usm_ndarray}
     Input array, expected to have a real-valued floating-point data type.
     Domain: [0, 2].
-out : {dpnp.ndarray, usm_ndarray}, optional
+out : {None, dpnp.ndarray, usm_ndarray, tuple of ndarray}, optional
     Optional output array for the function values.
+    A tuple (possible only as a keyword argument) must have length equal to the
+    number of outputs.
+
+    Default: ``None``.
 
 Returns
 -------