docs: def build_on_condition(self, runnable, regime, on_condition):
          """
          Build OnCondition event handler code.
  
          @param on_condition: OnCondition event handler object
          @type on_condition: lems.model.dynamics.OnCondition
  
          @return: Generated OnCondition code
          @rtype: list(string)
          """
  
          on_condition_code = []
  
          on_condition_code += ['if {0}:'.format(\
              self.build_expression_from_tree(runnable,
                                              regime,
                                              on_condition.expression_tree))]
  
          for action in on_condition.actions:
              code = self.build_action(runnable, regime, action)
              for line in code:
                  on_condition_code += ['    ' + line]
  
          return on_condition_code