CQI-104: fixed compiling regex pattern (#227)

core/tests.py

@@ -72,7 +72,7 @@ def test_save(self):
         #self.assertEquals(self.user.lastName, "Manal")
 
     def to_camel_case_key(self, input):
-        pattern = re.compile(r'(?<!^)(?=[A-Z]|[0-9]+)')
+        pattern = re.compile(r'(?<=[a-z0-9])(?=[A-Z])')
         if isinstance(input, list):
             res = []
             for elm in input: