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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 spkopa(filename):
 """ Open an existing SPK file for subsequent write. http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/spkopa_c.html :param filename: The name of an existing SPK file. :type filename: str :return: A handle attached to the SPK file opened to append. :rtype: int """

    filename = stypes.stringToCharP(filename)
    handle = ctypes.c_int()
    libspice.spkopa_c(filename, ctypes.byref(handle))
    return handle.value