<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def molmz(df, noise=10000):
 """ The mz of the molecular ion. """

    d = ((df.values > noise) * df.columns).max(axis=1)
    return Trace(d, df.index, name='molmz')