Parse observation types to simulation code
parse_obs_types(obs, initial = FALSE)specified observation object including at least a description of
which variable(s) are associated with a particular compartment, e.g.
list(variable="CONC", scale="1").
is this for the initial code block in the C++ template that
initializes the variables and compartments (TRUE), or for the
second code block used for the rest of the dataset?