In determining the meaning of any Act of Congress, unless the context indicates otherwise - words importing the singular include and apply to several persons, parties, or things; words importing the plural include the singular; words importing the masculine gender include the feminine as well; words used in the present tense include the future as well as the present; the words ''insane'' and ''insane person'' and ''lunatic'' shall include every idiot, lunatic, insane person, and person non compos mentis; the words ''person'' and ''whoever'' include corporations, companies, associations, firms, partnerships, societies, and joint stock companies, as well as individuals; ''officer'' includes any person authorized by law to perform the duties of the office; ''signature'' or ''subscription'' includes a mark when the person making the same intended it as such; ''oath'' includes affirmation, and ''sworn'' includes affirmed; ''writing'' includes printing and typewriting and reproductions of visual symbols by photographing, multigraphing, mimeographing, manifolding, or otherwise