omicverse.external.secact re-implements, in NumPy, the methods of

  SecAct  - R package, https://github.com/data2intelligence/SecAct (GPL-3.0)
  SecActpy - Python port, https://github.com/data2intelligence/SecActpy (MIT)

  Ru B, Gong L, Yang E, Park S, Zaki G, Aldape K, Wakefield L, Jiang P.
  Inference of secreted protein signaling activities in intercellular
  communication. Nat Methods 23, 1553-1563 (2026). doi:10.1038/s41592-026-03172-0

No source file of either package is copied. The SecAct/CytoSig signature
matrices and the auxiliary gene tables are not bundled: they are downloaded on
first use from the repositories above at pinned commits
(SecAct 8d9ce8355b3c7c05fff28f4dc3d393747a9f93cc,
 SecActpy 13bb6d2a6ff6ceffcb1c52f8dabccb3b3ebea6f3) and verified by SHA-256.
