docs: def convert_func(self, func):
          """
          Converts NeuroML arithmetic/logical functions to python equivalents.
  
          @param func: NeuroML function
          @type func: string
  
  
          @return: Python operator
          @rtype: string
          """
  
          if func == 'ln':
              return 'log'
          elif func == 'random':
              return 'random.uniform'
          elif func == 'H':
              def heaviside_step(x):
                  if x < 0: return 0
                  elif x > 0: return 1
                  else: return 0.5 
              return 'heaviside_step'
          else:
              return func