code: def ID_sch40(ND):
      
      myindex = (np.abs(np.array(pipedb['NDinch']) - (ND))).argmin()
      return (pipedb.iloc[myindex, 1] - 2*(pipedb.iloc[myindex, 5]))
docs: Return the inner diameter for schedule 40 pipes.
  
      The wall thickness for these pipes is in the pipedb.
  
      Take the values of the array, subtract the ND, take the absolute
      value, find the index of the minimium value.