code: def getCoeff(self, name, light=None, date=None):
          '''
          try to get calibration for right light source, but
          use another if they is none existent
          '''
          d = self.coeffs[name]
  
          try:
              c = d[light]
          except KeyError:
              try:
                  k, i = next(iter(d.items()))
                  if light is not None:
                      print(
                          'no calibration found for [%s] - using [%s] instead' % (light, k))
              except StopIteration:
                  return None
              c = i
          except TypeError:
              # coeff not dependent on light source
              c = d
          return _getFromDate(c, datef getCoeff(self, name, light=None, date=None):
          '''
          try to get calibration for right light source, but
          use another if they is none existent
          '''
          d = self.coeffs[name]
  
          try:
              c = d[light]
          except KeyError:
              try:
                  k, i = next(iter(d.items()))
                  if light is not None:
                      print(
                          'no calibration found for [%s] - using [%s] instead' % (light, k))
              except StopIteration:
                  return None
              c = i
          except TypeError:
              # coeff not dependent on light source
              c = d
          return _getFromDate(c, date)
docs: try to get calibration for right light source, but
          use another if they is none existent