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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 _interleaved_dtype( blocks: List[Block] ) -> Optional[Union[np.dtype, ExtensionDtype]]: """Find the common dtype for `blocks`. Parameters blocks : List[Block] Returns ------- dtype : Optional[Union[np.dtype, ExtensionDtype]] None is returned when `blocks` is empty. """

    if not len(blocks):
        return None

    return find_common_type([b.dtype for b in blocks])