<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def taint(taintedSet, taintedAttribute):
 u"""Adds an attribute to a set of attributes. Related attributes are also included."""

    taintedSet.add(taintedAttribute)
    if taintedAttribute == 'marker':
        taintedSet |= set(['marker-start', 'marker-mid', 'marker-end'])
    if taintedAttribute in ['marker-start', 'marker-mid', 'marker-end']:
        taintedSet.add('marker')
    return taintedSet