'Read in custom numeric formatting rules from the shared style table'

def parse_custom_num_formats(self):

    custom_formats = {}
    num_fmts = self.root.findall(('{%s}numFmts/{%s}numFmt' % (SHEET_MAIN_NS, SHEET_MAIN_NS)))
    for node in num_fmts:
        idx = int(node.get('numFmtId'))
        self.custom_number_formats[idx] = node.get('formatCode')
        self.number_formats.append(node.get('formatCode'))
