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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _migrate_subresources(parent, migrations):
 """ Migrate a resource's subresources :param parent: the parent perch.Document instance :param migrations: the migrations for a resource """

    for subresource, resource_migrations in migrations.items():
        parent = _migrate_subresource(
            subresource,
            parent,
            resource_migrations
        )

    return parent