Implements nin and nout for element-wise funcs

`nin` and `nout` properties return the number of arguments
to the function treated as inputs or outputs, respectively

Author: ndgrigorian

dpctl/tensor/_elementwise_common.py

@@ -93,6 +93,20 @@ def get_type_result_resolver_function(self):
         """
         return self.result_type_resolver_fn_
 
+    @property
+    def nin(self):
+        """
+        Returns the number of arguments treated as inputs.
+        """
+        return 1
+
+    @property
+    def nout(self):
+        """
+        Returns the number of arguments treated as outputs.
+        """
+        return 1
+
     @property
     def types(self):
         """Returns information about types supported by
@@ -531,6 +545,20 @@ def get_type_promotion_path_acceptance_function(self):
         """
         return self.acceptance_fn_
 
+    @property
+    def nin(self):
+        """
+        Returns the number of arguments treated as inputs.
+        """
+        return 2
+
+    @property
+    def nout(self):
+        """
+        Returns the number of arguments treated as outputs.
+        """
+        return 1
+
     @property
     def types(self):
         """Returns information about types supported by