<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def internal_classpath(cls, targets, classpath_products, confs=('default',)):
 """Return the list of internal classpath entries for a classpath covering all `targets`. Any classpath entries contributed by external dependencies will be omitted. :param targets: Targets to build an aggregated classpath for. :param ClasspathProducts classpath_products: Product containing classpath elements. :param confs: The list of confs for use by this classpath. :returns: The classpath as a list of path elements. :rtype: list of string """

    classpath_tuples = classpath_products.get_internal_classpath_entries_for_targets(targets)
    filtered_tuples_iter = cls._filtered_classpath_by_confs_iter(classpath_tuples, confs)
    return [entry.path for entry in cls._entries_iter(filtered_tuples_iter)]