code: def vlcom(a, v1, b, v2):
      
      v1 = stypes.toDoubleVector(v1)
      v2 = stypes.toDoubleVector(v2)
      sumv = stypes.emptyDoubleVector(3)
      a = ctypes.c_double(a)
      b = ctypes.c_double(b)
      libspice.vlcom_c(a, v1, b, v2, sumv)
      return stypes.cVectorToPython(sumv)
docs: Compute a vector linear combination of two double precision,
      3-dimensional vectors.
  
      http://naif.jpl.nasa.gov/pub/naif/toolkit_docs/C/cspice/vlcom_c.html
  
      :param a: Coefficient of v1 
      :type a: float
      :param v1: Vector in 3-space 
      :type v1: 3-Element Array of floats
      :param b: Coefficient of v2 
      :type b: float
      :param v2: Vector in 3-space 
      :type v2: 3-Element Array of floats
      :return: Linear Vector Combination a*v1 + b*v2.
      :rtype: 3-Element Array of floats