From the CHANGELOG:

• sicmutils.mechanics.lagrange/{Γ,Γ-bar} are removed in favor of the
  existing Gamma and Gamma-bar functions. The sicmutils.env aliases are
  gone as well.

• sicmutils.mechanics.lagrange/Lagrange-interpolation-function now returns
  an actual polynomial instance. Because polynomials support IFn and respond
  to the derivative operator D, this makes the find-path example on pages
  22/23 of SICM run about 5x faster.

• Richardson extrapolation is now implemented as a functional fold. The
  exposition in sicmutils.polynomial.richardson discusses this; the
  namespaces gains richardson-fold, richardson-sum and richardson-scan.