<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def line(line_def, **kwargs):
 """Highlights a character in the line"""

    def replace(s):
        return "(%s)" % ansi.aformat(s.group()[1:], attrs=["bold", ])
    return ansi.aformat(
        re.sub('@.?', replace, line_def),
        **kwargs)