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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 build_basic_auth(username: str, password: str) -> str: """ Build an Authorization header for HTTP Basic Auth. """

    # https://tools.ietf.org/html/rfc7617#section-2
    assert ":" not in username
    user_pass = f"{username}:{password}"
    basic_credentials = base64.b64encode(user_pass.encode()).decode()
    return "Basic " + basic_credentials