<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_displacement_rate( hazard, classification, hazard_class, qsettings=None):
 """Get displacement rate for hazard in classification in hazard class. :param hazard: The hazard key. :type hazard: basestring :param classification: The classification key. :type classification: basestring :param hazard_class: The hazard class key. :type hazard_class: basestring :param qsettings: A custom QSettings to use. If it's not defined, it will use the default one. :type qsettings: qgis.PyQt.QtCore.QSettings :returns: The value of displacement rate. If it's not affected, return 0. :rtype: int """

    is_affected_value = is_affected(
        hazard, classification, hazard_class, qsettings)
    if is_affected_value == not_exposed_class['key']:
        return 0  # Just to make it clear
    elif not is_affected_value:
        return 0
    preference_data = setting(
        'population_preference',
        default=generate_default_profile(),
        qsettings=qsettings)

    # Use default from the default profile
    default_profile = generate_default_profile()
    default_displacement_rate_value = default_profile.get(hazard, {}).get(
        classification, {}).get(hazard_class, {}).get('displacement_rate', 0)

    # noinspection PyUnresolvedReferences
    return preference_data.get(hazard, {}).get(classification, {}).get(
        hazard_class, {}).get(
        'displacement_rate', default_displacement_rate_value)