docs: def calc_lfp_layer(self):
          """
          Calculate the LFP from concatenated subpopulations residing in a
          certain layer, e.g all L4E pops are summed, according to the `mapping_Yy`
          attribute of the `hybridLFPy.Population` objects.
          """
          LFPdict = {}
  
          lastY = None
          for Y, y in self.mapping_Yy:
              if lastY != Y:
                  try:
                      LFPdict.update({Y : self.LFPdict[y]})
                  except KeyError:
                      pass
              else:
                  try:
                      LFPdict[Y] += self.LFPdict[y]
                  except KeyError:
                      pass
              lastY = Y
  
          return LFPdict