An idiom is a phrase used to represent something that has nothing to do with it and is not literal. For example: raining cats and dogs means it's raining hard and not literally raining animals. Seething with rage is not an idiom as seethe basically means mad or angry. Angry or mad with rage can be literal and is not an idiom.
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Writer constructs a diagram from data provided by others
Rule of thumb is that if it is from someone else and not your own mind, you should document it.
