docs: def acos(x, context=None):
      """
      Return the inverse cosine of ``x``.
  
      The mathematically exact result lies in the range [0, π].  However, note
      that as a result of rounding to the current context, it's possible for the
      actual value returned to be fractionally larger than π::
  
          >>> from bigfloat import precision
          >>> with precision(12):
          ...     x = acos(-1)
          ...
          >>> print(x)
          3.1416
          >>> x > const_pi()
          True
  
      """
      return _apply_function_in_current_context(
          BigFloat,
          mpfr.mpfr_acos,
          (BigFloat._implicit_convert(x),),
          context,
      )