pfa_cell: pfa_cell
In aurelius: Generates PFA Documents from R Code and Optionally Runs Them

Creates a list of lists representing a PFA cell.

1 2	pfa_cell(type, init, source = "embedded", shared = FALSE, rollback = FALSE)

`type`	cell type, which is an Avro schema as `list` of lists (created by avro_* functions)
`init`	cell initial value, which is a `list` of lists, usually converted from a model
`source`	if "embedded", the init is the data structure, if "json", the init is a URL string pointing to an external JSON file
`shared`	if TRUE, the cell is shared across scoring engine instances
`rollback`	if TRUE, the cell's value would be rolled back if an uncaught exception is encountered