Revert "#26 docstring update"

This reverts commit 71a6b1b7df6a5c55c614063dfce7f38bce3e656f.
Revert "typo fix"

This reverts commit 694007afa0bfc808954efd131847a5e0cca4ea33.
Revert "added invalid2nan function"

This reverts commit 5785b8106dac9a52ab4534e0c7bf11af30a02198.