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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 configure_once(config=None, bind_in_runtime=True):
 """Create an injector with a callable config if not present, otherwise, do nothing."""

    with _INJECTOR_LOCK:
        if _INJECTOR:
            return _INJECTOR

        return configure(config, bind_in_runtime=bind_in_runtime)