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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 from_text(text):
 """Convert text into an rcode. @param text: the texual rcode @type text: string @raises UnknownRcode: the rcode is unknown @rtype: int """


    if text.isdigit():
        v = int(text)
        if v >= 0 and v <= 4095:
            return v
    v = _by_text.get(text.upper())
    if v is None:
        raise UnknownRcode
    return v