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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 make_unique_str(num_chars=20):
 """make a random string of characters for a temp filename"""

    chars = 'abcdefghigklmnopqrstuvwxyz'
    all_chars = chars + chars.upper() + '01234567890'
    picks = list(all_chars)
    return ''.join([choice(picks) for i in range(num_chars)])