This recursive methods creates a tree of scidb.expression objects corresponding to the R expression supplied as a parameter.
R variables can be interpolated into the expression by prepending them with the double-exclamation !! operator.
In addition to base R unary and binary operands, this method treats several operations as special cases, and also defines several custom operations of its own that can be used: * ` only be used when the RHS value is a non-symbolic scalar or vector value * ` * ` operands are treated as special cases of the regex function `stringr::str_detect`, and can be applied to symbolic and non-symbolic arguments