<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def total_level(source_levels):
 """ Calculates the total sound pressure level based on multiple source levels """

    sums = 0.0
    for l in source_levels:
        if l is None:
            continue
        if l == 0:
            continue
        sums += pow(10.0, float(l) / 10.0)
    level = 10.0 * math.log10(sums)
    return level