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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 encode(number, alphabet):
 """ Converts an integer to a base n string where n is the length of the provided alphabet. Modified from http://en.wikipedia.org/wiki/Base_36 """

    if not isinstance(number, (int, long)):
        raise TypeError("Number must be an integer.")

    base_n = ""
    sign = ""

    if number < 0:
        sign = "-"
        number = -number

    if 0 <= number < len(alphabet):
        return sign + alphabet[number]

    while number != 0:
        number, i = divmod(number, len(alphabet))
        base_n = alphabet[i] + base_n

    return sign + base_n