import base64


def from_base64(base64_string):
    """
    Decodes the given base-64 string to a byte array.

    :param base64_string: A base-64 encoded string.
    :return: The decoded byte array.
    """
    result = None
    if base64_string is not None:
        result = bytearray(base64.b64decode(base64_string))
    return result