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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 get_from_environment():
    '''
        Return the JavaScript runtime that is specified in EXECJS_RUNTIME environment variable.
        If EXECJS_RUNTIME environment variable is empty or invalid, return None.
    '''
    name = os.environ.get("EXECJS_RUNTIME", "")
    if not name:
        return None

    try:
        return _find_runtime_by_name(name)
    except exceptions.RuntimeUnavailableError:
        return None