code: def append(self, other):
          
          if not isinstance(other,StarPopulation):
              raise TypeError('Only StarPopulation objects can be appended to a StarPopulation.')
          if not np.all(self.stars.columns == other.stars.columns):
              raise ValueError('Two populations must have same columns to combine them.')
  
          if len(self.constraints) > 0:
              logging.warning('All constraints are cleared when appending another population.')
  
          self.stars = pd.concat((self.stars, other.stars))
  
          if self.orbpop is not None and other.orbpop is not None:
              self.orbpop = self.orbpop + other.orbpop
docs: Appends stars from another StarPopulations, in place.
  
          :param other:
              Another :class:`StarPopulation`; must have same columns as ``self``.