Papers, books, accounts, documents, testimony, and records sought in accordance with a subpoena issued under § 2–408, § 2–507, § 2–807, § 2–1104, or § 2–1608 of this title in connection with a lawfully authorized legislative inquiry or examination must be pertinent to the inquiry or examination. For purposes of subsection (a) of this section, papers, books, accounts, documents, testimony, or records are considered pertinent if they: relate to the matters under inquiry or examination; assist in assessing the credibility of a witness; contradict or corroborate the testimony of a witness; or demonstrate the existence of undue influence on a witness.