This provides a reticulate engine for knitr, suitable for usage when
attempting to render Python chunks. Using this engine allows for shared state
between Python chunks in a document -- that is, variables defined by one
Python chunk can be used by later Python chunks.
eng_python(options)Chunk options, as provided by knitr during chunk execution.
The engine can be activated by setting (for example)
knitr::knit_engines$set(python = reticulate::eng_python)
Typically, this will be set within a document's setup chunk, or by the environment requesting that Python chunks be processed by this engine.