code: def extrusion(target, throat_length='throat.length',
                throat_area='throat.area'):
      r
      leng = target[throat_length]
      area = target[throat_area]
      value = leng*area
      return value
docs: r"""
      Calculate throat volume from the throat area and the throat length. This
      method is useful for abnormal shaped throats.
  
      Parameters
      ----------
      target : OpenPNM Object
          The object which this model is associated with. This controls the
          length of the calculated array, and also provides access to other
          necessary properties.
  
      throat_length and throat_area : strings
          The dictionary keys containing the arrays with the throat area and
          length values.
  
      Notes
      -----
      At present this models does NOT account for the volume reprsented by the
      intersection of the throat with a spherical pore body.