'Formats the KeyVaultIdentifier into a identifier uri based of the specified format string
:param fmt: The format string for the identifier uri
:return: The formatted key vault object identifier uri'

def _format(self, fmt=None):

    fmt = (fmt or self._id_format)
    segments = []
    for fmt_seg in fmt.split('/'):
        if (fmt_seg.startswith('{') and fmt_seg.endswith('}')):
            fmt_seg = fmt_seg[1:(-1)]
            fmt_prop = fmt_seg.rstrip('?')
            seg_val = getattr(self, fmt_prop)
            if seg_val:
                segments.append(seg_val.strip('/').strip())
            elif (not fmt_seg.endswith('?')):
                raise ValueError('invalid    id:    No    value    specified    for    the    required    segment    "{}"'.format(fmt_prop))
        else:
            segments.append(fmt_seg)
    return '/'.join(segments)
