def withdraw(key, to_address, amount=None, dst_tag=None):
keypair = RawKeypair(key)
builder = Builder(address=public_key_to_address(keypair.raw_public_key()),
network='PUBLIC')
if amount is None:
builder.append_account_merge_op(to_address)
else:
builder.append_payment_op(to_address, str(round(float(amount), 7)),
'XLM')
if dst_tag is not None:
builder.add_text_memo(dst_tag)
builder.keypair = keypair
builder.sign()
ret = builder.submit()
if ret['successful']:
return ret['hash']
print(ret)
return None
