code: function cleanContractCalls () {
    return new Promise((resolve, reject) => {
      enqueueAction(
        this,
        (channel, state) => state.handler === handlers.channelOpen,
        (channel, state) => {
          send(channel, {
            jsonrpc: '2.0',
            method: 'channels.clean_contract_calls',
            params: {}
          })
          return {
            handler: handlers.awaitingCallsPruned,
            state: { resolve, reject }
          }
        }
      )
    })
  }
docs: Clean up all locally stored contract calls
  
  Contract calls are kept locally in order for the participant to be able to look them up.
  They consume memory and in order for the participant to free it - one can prune all messages.
  This cleans up all locally stored contract calls and those will no longer be available for
  fetching and inspection.
  
  @return {Promise}