code: def ramp(time, slope, start, finish=0):
      
  
      t = time()
      if t < start:
          return 0
      else:
          if finish <= 0:
              return slope * (t - start)
          elif t > finish:
              return slope * (finish - start)
          else:
              return slope * (t - start)
docs: Implements vensim's and xmile's RAMP function
  
      Parameters
      ----------
      time: function
          The current time of modelling
      slope: float
          The slope of the ramp starting at zero at time start
      start: float
          Time at which the ramp begins
      finish: float
          Optional. Time at which the ramp ends
  
      Returns
      -------
      response: float
          If prior to ramp start, returns zero
          If after ramp ends, returns top of ramp
      Examples
      --------