def set_exists(policy, key)
      begin_cmd
      field_count = estimate_key_size(key)
      size_buffer
      write_header(policy, INFO1_READ|INFO1_NOBINDATA, 0, field_count, 0)
      write_key(key)
      end_cmd
    end
def set_exists(policy, key)
      begin_cmd
      field_count = estimate_key_size(key)
      size_buffer
      write_header(policy, INFO1_READ|INFO1_NOBINDATA, 0, field_count, 0)
      write_key(key)
      end_cmd
    end
Writes the command for exist operations