Make.CMval init : epsilon:float -> delta:float -> 'a sketch``init epsilon delta`` initializes a sketch with approximation ratio ``(1 + epsilon)`` and failure probability ``delta``.
val incr : 'a sketch -> 'a -> unit``incr s x`` increments the frequency count of ``x`` in sketch ``s`` in-place.
val count : 'a sketch -> 'a -> int``count s x`` returns the estimated frequency of element ``x`` in ``s``.
``init_from s`` initializes a new empty sketch with the same parameters as ``s``, which can later be merged with ``s``.