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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def merge_datetime(date, time='', date_format='%d/%m/%Y', time_format='%H:%M'):
 """Create ``datetime`` object from date and time strings."""

    day = datetime.strptime(date, date_format)
    if time:
        time = datetime.strptime(time, time_format)
        time = datetime.time(time)
        day = datetime.date(day)
        day = datetime.combine(day, time)
    return day