Character string, an XPath identifying R code to lint.
See xmlparsedata::xml_parse_data() and get_source_expressions().
lint_message
The message to be included as the message
to the Lint object. If lint_message is a character vector the same length as xml,
the i-th lint will be given the i-th message.
type
type of lint.
level
Which level of expression is being tested? "expression"
means an individual expression, while "file" means all expressions
in the current file are available.