docs: def write_elec_file(filename, mesh):
      """
      Read in the electrode positions and return the indices of the electrodes
  
      # TODO: Check if you find all electrodes
      """
      elecs = []
      # print('Write electrodes')
      electrodes = np.loadtxt(filename)
      for i in electrodes:
          # find
          for nr, j in enumerate(mesh['nodes']):
              if np.isclose(j[1], i[0]) and np.isclose(j[2], i[1]):
                  elecs.append(nr + 1)
  
      fid = open('elec.dat', 'w')
      fid.write('{0}\n'.format(len(elecs)))
      for i in elecs:
          fid.write('{0}\n'.format(i))
      fid.close()