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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 is_path(path):
 """Checks if the passed in path is a valid Path within the portal :param path: The path to check :type uid: string :return: True if the path is a valid path within the portal :rtype: bool """

    if not isinstance(path, basestring):
        return False
    portal_path = get_path(get_portal())
    if not path.startswith(portal_path):
        return False
    obj = get_object_by_path(path)
    if obj is None:
        return False
    return True