@classmethod
def fromkeys(cls, **kwargs):
    """Initialise a header from parsed values.

        Like :meth:`~baseband.vdif.VDIFHeader.fromvalues`, but without any
        interpretation of keywords.

        Raises
        ------
        KeyError : if not all keys required are pass in.
        """
    edv = False if kwargs['legacy_mode'] else kwargs['edv']
    return super().fromkeys(edv, **kwargs)
