def _interleaved_dtype(<EOL>blocks: List[Block]<EOL>) -> Optional[Union[np.dtype, ExtensionDtype]]:
if not len(blocks):<EOL><INDENT>return None<EOL><DEDENT>return find_common_type([b.dtype for b in blocks])<EOL>
Find the common dtype for `blocks`.

    Parameters
    ----------
    blocks : List[Block]

    Returns
    -------
    dtype : Optional[Union[np.dtype, ExtensionDtype]]
        None is returned when `blocks` is empty.