code: func (s *FuncMovingAverage) Signature() ([]Arg, []Arg) {
  	return []Arg{
  		ArgSeriesList{val: &s.in},
  		// this could be an int OR a string.
  		// we need to figure out the interval of the data we will consume
  		// and request from -= interval * points
  		// interestingly the from adjustment might mean the archive TTL is no longer sufficient and push the request into a different rollup archive, which we should probably
  		// account for. let's solve all of this later.
  		ArgInt{val: &s.window},
  	}, []Arg{ArgSeriesList{}}
  }
docs: // note if input is 1 series, then output is too. not sure how to communicate that