Helper for determining whether the current source_expression contains
all expressions in the current file, or just a single expression.
is_lint_level(source_expression, level = c("expression", "file"))A parsed expression object, i.e., an element
of the object returned by get_source_expressions().
Which level of expression is being tested? "expression"
means an individual expression, while "file" means all expressions
in the current file are available.