Reverting of removing callable provider example

examples/providers/callable.py

@@ -0,0 +1,40 @@
+"""`Callable` providers examples."""
+
+from objects.providers import Callable
+from objects.injections import KwArg
+
+
+class SomeCrypt(object):
+
+    """Example class SomeCrypt."""
+
+    @staticmethod
+    def encrypt(data, password):
+        """Encypt data using password."""
+        return ''.join((password, data, password))
+
+    @staticmethod
+    def decrypt(data, password):
+        """Decrypt data using password."""
+        return data[len(password):-len(password)]
+
+
+# Encrypt and decrypt function providers:
+encrypt = Callable(SomeCrypt.encrypt,
+                   KwArg('password', 'secret123'))
+decrypt = Callable(SomeCrypt.decrypt,
+                   KwArg('password', 'secret123'))
+
+# Making some asserts:
+initial_data = 'some_data'
+
+encrypted1 = encrypt(initial_data)
+decrypted1 = decrypt(encrypted1)
+
+assert decrypted1 == initial_data
+
+# Context keyword arguments priority example:
+encrypted2 = encrypt(initial_data, password='another_secret')
+decrypted2 = decrypt(encrypted2)
+
+assert decrypted2 != initial_data