Return true if the string is a valid filename.

Return true if the string is a valid identifier.

NewLabel returns a new label which is a concatenation of the prefix and parts, separated by a period.

An file is a string which starts with a letter or number and is followed by letters, numbers, underscores or hyphens and punkts.

An identifier is a string which starts with a letter and is followed by letters, numbers, underscores or hyphens.