This function generates all possible combinations of keys from a given named list or vector.
Examples
if (FALSE) { # \dontrun{
criteria <- list(key1 = "value1", key2 = "value2", key3 = "value3")
get_combinations(criteria)
# Returns a list of combinations: c("key1"), c("key2"), c("key3"), c("key1", "key2"), ...
} # }