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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 with_start_after(self, after_namespace):
 """Returns a copy of this NamespaceName with a new namespace_start. Args: after_namespace: A namespace string. Returns: A NamespaceRange object whose namespace_start is the lexographically next namespace after the given namespace string. Raises: ValueError: if the NamespaceRange includes only a single namespace. """

    namespace_start = _ord_to_namespace(_namespace_to_ord(after_namespace) + 1)
    return NamespaceRange(namespace_start, self.namespace_end, _app=self.app)