Is this thread unsafe?

gistfile1.py

class Foo(object):
    def __init__(self, client):
        self._cache = {}
        self.client = client

    def get():
        client.get_from_server()

class Bar(object):
    def __init__(self, client):
        self._cache = {}
        self.client = client

    def get():
        client.get_from_server()

client = Client("http://foo.com/sdk")
f = Foo(client)
b = Bar(client)