<b>Not a bug, just English suggestion:</b> The word "operate" is a verb (i.e. action) and "type" is a attributive noun (kind of like an adjective), but not being used as the phrase subject, so it  can't modify the verb.  I'm told and I can understand this is a _very_ difficult aspect of English language, so I am extra tolerant :)

Normally the "subject" part of a function/method parameter names are nouns, sometimes paired with a verb or adjective.  But there must always be a main "subject". In this case the intended subject is "operation" (a noun, meaning what is being done) and it is modified by "type" (description of how something is being done).  But programmers are usually lazy and would just abbreviate this as "op_type", where op == operation.