fail_if_not_found       Return a failing grade based on the result of a
                        find function
find_argument_values    Find the values of arguments in R code
find_arguments          Find arguments in R code
find_arithmetic         Find arithmetic operators in R code
find_assigns            Find assignments in R code
find_comparisons        Find comparison operators in R code
find_extractions        Find extraction operators in R code
find_functions          Find functions in R code
find_infixes            Find infixes in R code
find_lhs                Find the left- or right-hand side of an
                        operator in R code
find_logical_operators
                        Find logical operators in R code
find_objects            Find objects in R code
find_operators          Find operators in R code
find_parent             Find the parent of an expression in R code
find_pipes              Find pipes in R code
standardize_arguments   Standardize arguments to function calls
