code: def coerce(cls, key, value):
          
  
          if isinstance(value, string_types):
              value = value.strip()
              if value[0] == '[':  # It's json encoded, probably
                  try:
                      value = json.loads(value)
                  except ValueError:
                      raise ValueError("Failed to parse JSON: '{}' ".format(value))
              else:
                  value = value.split(',')
  
          if not value:
              value = []
  
          self = MutationList((MutationObj.coerce(key, v) for v in value))
          self._key = key
          return self
docs: Convert plain list to MutationList.