code: def email_addresses2marc(self, key, value):
      
      m_or_o = 'm' if value.get('current') else 'o'
      element = {
          m_or_o: value.get('value')
      }
  
      if value.get('hidden'):
          return element
      else:
          self.setdefault('371', []).append(element)
          return None
docs: Populate the 595 MARCXML field.
  
      Also populates the 371 field as a side effect.