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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 getMd5Checksum(self):
 """ Returns the MD5 checksum for this reference set. This checksum is calculated by making a list of `Reference.md5checksum` for all `Reference`s in this set. We then sort this list, and take the MD5 hash of all the strings concatenated together. """

        references = sorted(
            self.getReferences(),
            key=lambda ref: ref.getMd5Checksum())
        checksums = ''.join([ref.getMd5Checksum() for ref in references])
        md5checksum = hashlib.md5(checksums).hexdigest()
        return md5checksum