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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 _getsize_from_header(self, header):
 """ Return the size from header Args: header (dict):
 Object header. Returns: int: Size in bytes. """

        # By default, assumes that information are in a standard HTTP header
        for key in self._SIZE_KEYS:
            try:
                return int(header.pop(key))
            except KeyError:
                continue
        else:
            raise UnsupportedOperation('getsize')