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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 parse_format(self):
 """Check format parameter. All formats values listed in the specification are lowercase alphanumeric value commonly used as file extensions. To leave opportunity for extension here just do a limited sanity check on characters and length. """

        if (self.format is not None and
                not re.match(r'''\w{1,20}$''', self.format)):
            raise IIIFRequestError(
                parameter='format',
                text='Bad format parameter')