@property<EOL><INDENT>def sample_subannotation(self):<DEDENT>
warnings.warn("<STR_LIT>".<EOL>format(OLD_SUBS_META_KEY, SAMPLE_SUBANNOTATIONS_KEY),<EOL>DeprecationWarning)<EOL>return getattr(self, SAMPLE_SUBANNOTATIONS_KEY)<EOL>
Return the data table that stores metadata for subsamples/units.

:return pandas.core.frame.DataFrame | NoneType: table of
    subsamples/units metadata