add support for import module custom functions

test/data/custom_functions.py

@@ -0,0 +1,42 @@
+import hashlib
+import json
+import random
+import string
+
+try:
+    string_type = basestring
+    PYTHON_VERSION = 2
+except NameError:
+    string_type = str
+    PYTHON_VERSION = 3
+
+
+def gen_random_string(str_len):
+    return ''.join(
+        random.choice(string.ascii_letters + string.digits) for _ in range(str_len))
+
+def gen_md5(*args):
+    args = [handle_req_data(item) for item in args]
+    return hashlib.md5("".join(args).encode('utf-8')).hexdigest()
+
+def handle_req_data(data):
+
+    if PYTHON_VERSION == 3 and isinstance(data, bytes):
+        # In Python3, convert bytes to str
+        data = data.decode('utf-8')
+
+    if not data:
+        return data
+
+    if isinstance(data, str):
+        # check if data in str can be converted to dict
+        try:
+            data = json.loads(data)
+        except ValueError:
+            pass
+
+    if isinstance(data, dict):
+        # sort data in dict with keys, then convert to str
+        data = json.dumps(data, sort_keys=True)
+
+    return data