<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def text_colour_for_hex(hexx, percent=50, dark='#000000', light='#ffffff'):
 """ Function to decide what colour to use for a given hex colour. Args: hexx (str):
 A hexadecimal colour, starting with '#'. Returns: bool: The colour's brightness is less than the given percent. """

    return light if hex_is_dark(hexx, percent=percent) else dark