code: def _EncodeInt64Field(field, value):
      
      capabilities = [
          messages.Variant.INT64,
          messages.Variant.UINT64,
      ]
      if field.variant not in capabilities:
          return encoding.CodecResult(value=value, complete=False)
  
      if field.repeated:
          result = [str(x) for x in value]
      else:
          result = str(value)
      return encoding.CodecResult(value=result, complete=True)
docs: Handle the special case of int64 as a string.