hash_params documentation added

README.rst

@@ -130,6 +130,18 @@ Sometimes you may want your function to trigger a calculation when it encounters
 Further function calls made while the calculation is being performed will not trigger redundant calculations.
 
 
+Working with unhashable arguments
+---------------------------------
+
+As mentioned above, The positional and keyword arguments to the wrapped function must be hashable (i.e. Python's immutable built-in objects, not mutable containers). To get around this limitation the ``hash_params`` parameter of the ``cachier`` decorator can be provided with a callable that gets the args and kwargs from the decorated function and returns a hash key for them.
+
+.. code-block:: python
+
+  @cachier(hash_params=hash_my_custom_class)
+  def calculate_super_complex_stuff(custom_obj):
+    # amazing code goes here
+
+
 Per-function call arguments
 ---------------------------
 

cachier/core.py

@@ -114,10 +114,10 @@ def cachier(
         The running process must have running permissions to this folder. If
         not provided, a default directory at `~/.cachier/` is used.
     hash_params : callable, optional
-        A callable that takes args and kwargs from main function and returns
-        a hash key of these params. If unset, default transformation is
-        applied. It is valuable and works as workaround in scenarios
-        that positional and keyword arguments are not hashable.
+        A callable that gets the args and kwargs from the decorated function
+        and returns a hash key for them. This parameter can be used to enable
+        the use of cachier with functions that get arguments that are not
+        automatically hashable by Python.
     """
     # print('Inside the wrapper maker')
     # print('mongetter={}'.format(mongetter))