At Datadog, performance counters are emitted as log lines in the format name=value. Write a function that parses a list of counter strings and flags anomalous counters based on recent history.
A line is valid only if it contains exactly one = and the value is a valid integer. Ignore invalid lines. For each counter name, keep the sequence of parsed values in input order. A counter value is considered anomalous if it is at least threshold greater than the average of the previous window_size valid values for the same counter. If fewer than window_size previous values exist for that counter, do not evaluate anomaly status for that occurrence.
Return a list of anomalies in the order they are detected. Each anomaly should be represented as [name, index, value], where index is the original position in the input list.
lines as a list of strings, window_size as an integer, threshold as an integer[counter_name, original_index, counter_value]def flag_counter_anomalies(lines, window_size, threshold):