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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 all_tamil( word_in ):
 """ predicate checks if all letters of the input word are Tamil letters """

    if isinstance(word_in,list):
        word = word_in
    else:
        word = get_letters( word_in )
    return all( [(letter in tamil_letters) for letter in word] )