human
Complete the below
def _sequence_field(checked_class, suffix, item_type, optional, initial):

    ''''Create checked field for either ``PSet`` or ``PVector``.
    :param checked_class: ``CheckedPSet`` or ``CheckedPVector``.
    :param suffix: Suffix for new type name.
    :param item_type: The required type for the items in the set.
    :param bool optional: If true, ``None`` can be used as a value for
    this field.
    :param initial: Initial value to pass to factory.
    :return: A ``field`` containing a checked class.'
    '''
assistant
#Here is Python code to fix for new type name.
    class TheType(checked_class, ):
        __type__ = item_type
    TheType.__name__ = (item_type.__name__.capitalize() + suffix)
    if optional:
        def factory(argument):
            if (argument is None):
                return None
            else:
                return TheType(argument)
    else:
        factory = TheType
    return field(type=(optional_type(TheType) if optional else TheType), factory=factory, mandatory=True, initial=factory(initial))