Added tests and docstring to exchange funding_fee methods, removed utils

tests/exchange/test_ftx.py

@@ -1,3 +1,4 @@
+from datetime import datetime, timedelta
 from random import randint
 from unittest.mock import MagicMock
 
@@ -191,3 +192,18 @@ def test_get_order_id(mocker, default_conf):
         }
     }
     assert exchange.get_order_id_conditional(order) == '1111'
+
+
+@pytest.mark.parametrize("pair,when", [
+    ('XRP/USDT', datetime.utcnow()),
+    ('ADA/BTC', datetime.utcnow()),
+    ('XRP/USDT', datetime.utcnow() - timedelta(hours=30)),
+])
+def test__get_funding_rate(default_conf, mocker, pair, when):
+    api_mock = MagicMock()
+    exchange = get_patched_exchange(mocker, default_conf, api_mock, id="ftx")
+    assert exchange._get_funding_rate(pair, when) is None
+
+
+def test__get_funding_fee():
+    return