Python Click CLI: Validate and Modify Arguments

Click arguments validation and modify arguments.

Symbol must be BTCUSDT, ETHUSDT, BTCETH as per this rule.
Split symbol from BTCUSDT into BTC and USDT.

import clickimport redef validate_symbol(ctx, param, value):    m = re.search(r'^(\w+)(BTC|ETH|BNB|USDT|PAX|TUSD|USDC)$', value)    if m:        c1_symbol = m.group(1)        c2_symbol = m.group(2)        return (c1_symbol, c2_symbol)    else:        raise click.BadParameter('Invalid symbol')@cli.command()@click.option('--symbol', callback=validate_symbol, required=True)def get_price(symbol):    c1_symbol, c2_symbol = symbol    symbol = ''.join(symbol)