When I use "wss://node.bitshares.eu" (live node)

from bitshares import BitShares
bitshares = BitShares()
bitshares.wallet.unlock("secret word")
bitshares.transfer("red-head", "1", "BTS","memo details here",None)  --> **This is working**

When I use "wss://node.testnet.bitshares.eu" (testnet node)

from bitshares import BitShares
bitshares = BitShares()
bitshares.wallet.unlock("secret word")
bitshares.transfer("red-head", "1", "TEST","memo details here",None)  --> **This is NOT WORKING**

Here is the error details ;

Traceback (most recent call last):
File "/home/serdar/bitshares-deneme.py", line 46, in
print(bitshares.transfer("testt1", "1", "MYBTC","deneme",None))
File "/home/serdar/.local/lib/python3.5/site-packages/bitshares/bitshares.py", line 429, in transfer
"prefix": self.rpc.chain_params["prefix"]
File "/home/serdar/.local/lib/python3.5/site-packages/bitsharesbase/operations.py", line 46, in init
memo = Optional(Memo(kwargs["memo"]))
File "/home/serdar/.local/lib/python3.5/site-packages/bitsharesbase/objects.py", line 98, in init
('from', PublicKey(kwargs["from"], prefix=prefix)),
File "/home/serdar/.local/lib/python3.5/site-packages/bitsharesbase/account.py", line 84, in init
super(PublicKey, self).init(*args, **kwargs)
File "/home/serdar/.local/lib/python3.5/site-packages/graphenebase/account.py", line 216, in init
self._pk = Base58(pk, prefix=prefix)
File "/home/serdar/.local/lib/python3.5/site-packages/graphenebase/base58.py", line 60, in init
raise ValueError("Error loading Base58 object")
ValueError: Error loading Base58 object