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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 pxform(fromstr, tostr, et):
 """ Return the matrix that transforms position vectors from one specified frame to another at a specified epoch. http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/pxform_c.html :param fromstr: Name of the frame to transform from. :type fromstr: str :param tostr: Name of the frame to transform to. :type tostr: str :param et: Epoch of the rotation matrix. :type et: float :return: A rotation matrix. :rtype: 3x3 Element Array of floats """

    et = ctypes.c_double(et)
    tostr = stypes.stringToCharP(tostr)
    fromstr = stypes.stringToCharP(fromstr)
    rotatematrix = stypes.emptyDoubleMatrix()
    libspice.pxform_c(fromstr, tostr, et, rotatematrix)
    return stypes.cMatrixToNumpy(rotatematrix)