def get_constr_expr(lh_op, rh_op):
 if (rh_op is None):
  return lh_op
 else:
  return sum_expr([lh_op, neg_expr(rh_op)])

def get_constr_expr ( lh_op , rh_op ) : if ( rh_op is None ) : return lh_op else : return sum_expr ( [ lh_op , neg_expr ( rh_op ) ] )
returns the operator in the constraint .