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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 get_username_max_len():
 """Returns username maximum length as supported by Django. :rtype: int """

    fields = [field for field in USER._meta.fields if field.name == 'username']
    try:
        length = fields[0].max_length
    except IndexError:
        length = 30
    return length