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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _resolve_username(self, account, username):
 """Resolve username and handle deprecation of account kwarg"""

        if account is not None:
            warnings.warn(
                "Use keyword argument 'username' instead of 'account'",
                DeprecationWarning)
        return username or account or self.username