first custom tag seriliazer tests

utils/tag_serializers.py

@@ -0,0 +1,39 @@
+from rest_framework import serializers
+
+
+
+class SingleTag(str):
+
+    def __init__(self, *args, **kwargs):
+        pass
+
+    def __str__(self):
+        return self
+
+
+class SingleTagSerializerField(serializers.Field):
+    child = serializers.CharField()
+    default_error_messages = {
+        'not_a_str': 'Expected a string but got type "{input_type}".',
+    }
+    order_by = None
+
+    def __init__(self, **kwargs):
+        super(SingleTagSerializerField, self).__init__(**kwargs)
+
+    def to_internal_value(self, value):
+        if isinstance(value, str):
+            if not value:
+                value = ""
+
+        if not isinstance(value, str):
+            self.fail('not_a_str', input_type=type(value).__name__)
+
+        return value
+
+    def to_representation(self, value):
+        if not isinstance(value, SingleTag):
+            if not isinstance(value, str):
+                value = value.name
+            value = SingleTag(value)
+        return value