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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 setFormatMetadata(self, format):
 """ Set format image metadata to what has been reliably identified. """

    assert((self.needMetadataUpdate(CoverImageMetadata.FORMAT)) or
           (self.format is format))
    self.format = format
    self.check_metadata &= ~CoverImageMetadata.FORMAT