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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 validate_scopes(value_list):
 """Validate if each element in a list is a registered scope. :param value_list: The list of scopes. :raises invenio_oauth2server.errors.ScopeDoesNotExists: The exception is raised if a scope is not registered. :returns: ``True`` if it's successfully validated. """

    for value in value_list:
        if value not in current_oauth2server.scopes:
            raise ScopeDoesNotExists(value)
    return True