code: def pltexp(iverts, delta):
      
      iverts = stypes.toDoubleMatrix(iverts)
      delta = ctypes.c_double(delta)
      overts = stypes.emptyDoubleMatrix()
      libspice.pltexp_c(iverts, delta, overts)
      return stypes.cMatrixToNumpy(overts)
docs: Expand a triangular plate by a specified amount. The expanded 
      plate is co-planar with, and has the same orientation as, the 
      original. The centroids of the two plates coincide. 
      
      https://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/pltexp_c.html
      
      :param iverts: Vertices of the plate to be expanded. 
      :type iverts: 3x3-Element Array of floats
      :param delta: Fraction by which the plate is to be expanded.
      :type delta: double
      :return: Vertices of the expanded plate. 
      :rtype: 3x3-Element Array of floats