'Return a list of PanLex language varieties.
:param lc: ISO 639 alpha-3 code. If specified, filters returned varieties
by this code. If unspecified, all varieties are returned.
:return: the specified language varieties as a list of tuples. The first
element is the language variety\'s seven-character uniform identifier,
and the second element is its default name.
:rtype: list(tuple)'

def language_varieties(self, lc=None):

    if (lc == None):
        return self._c.execute('SELECT    uid,    tt    FROM    lv    ORDER    BY    uid').fetchall()
    else:
        return self._c.execute('SELECT    uid,    tt    FROM    lv    WHERE    lc    =    ?    ORDER    BY    uid', (lc,)).fetchall()
