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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 on_windows ():
 """ Returns true if running on windows, whether in cygwin or not. """

    if bjam.variable("NT"):
        return True

    elif bjam.variable("UNIX"):

        uname = bjam.variable("JAMUNAME")
        if uname and uname[0].startswith("CYGWIN"):
            return True

    return False