code: def mw(self):
          '''Calculate the molecular weight.
  
          :returns: The molecular weight of the current sequence in amu.
          :rtype: float
  
          '''
          counter = collections.Counter(self.seq.lower())
          mw_a = counter['a'] * 313.2
          mw_t = counter['t'] * 304.2
          mw_g = counter['g'] * 289.2
          mw_c = counter['c'] * 329.2
          mw_u = counter['u'] * 306.2
  
          if self.material == 'dna':
              return mw_a + mw_t + mw_g + mw_c + 79.0
          else:
              return mw_a + mw_u + mw_g + mw_c + 159.f mw(self):
          '''Calculate the molecular weight.
  
          :returns: The molecular weight of the current sequence in amu.
          :rtype: float
  
          '''
          counter = collections.Counter(self.seq.lower())
          mw_a = counter['a'] * 313.2
          mw_t = counter['t'] * 304.2
          mw_g = counter['g'] * 289.2
          mw_c = counter['c'] * 329.2
          mw_u = counter['u'] * 306.2
  
          if self.material == 'dna':
              return mw_a + mw_t + mw_g + mw_c + 79.0
          else:
              return mw_a + mw_u + mw_g + mw_c + 159.0
docs: Calculate the molecular weight.
  
          :returns: The molecular weight of the current sequence in amu.
          :rtype: float