old_contents: 
  class FragmentReaction(object):
  
  	def __init__(self,
  				index=-1,
  				reactants=None,
  				products=None,
  				kinetics=None,
  				reversible=False,
  				pairs=None,
  				family=None
  				):
  
  		
  		self.index = index
  		self.reactants = reactants
  		self.products = products
  		self.kinetics = kinetics
  		self.reversible = reversible
  		self.pairs = pairs
  		self.family = family
  	
  	def __str__(self):
  		"""
  		Return a string representation of the reaction, in the form 'A + B <=> C + D'.
  		"""
  		arrow = ' <=> '
  		if not self.reversible: arrow = ' => '
  		return arrow.join([' + '.join([str(s) for s in self.reactants]), ' + '.join([str(s) for s in self.products])])
  
new_contents: 
  class FragmentReaction(object):
  
  	def __init__(self,
  				index=-1,
  				reactants=None,
  				products=None,
  				kinetics=None,
  				reversible=False,
  				pairs=None,
  				family=None,
  				reaction_repr=None
  				):
  
  		
  		self.index = index
  		self.reactants = reactants
  		self.products = products
  		self.kinetics = kinetics
  		self.reversible = reversible
  		self.pairs = pairs
  		self.family = family
  		self.reaction_repr = reaction_repr
  	
  	def __str__(self):
  		"""
  		Return a string representation of the reaction, in the form 'A + B <=> C + D'.
  		"""
  		arrow = ' <=> '
  		if not self.reversible: arrow = ' => '
  		return arrow.join([' + '.join([str(s) for s in self.reactants]), ' + '.join([str(s) for s in self.products])])
  
subject: add reaction_repr attribute for fragment reaction