code: def pxform(fromstr, tostr, et):
      
      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)
docs: 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