def METHOD_NAME(self, value):
    """Insert an occurrence of `value` into the btree."""
    i = 0
    n = len(self._tree)
    while i < n:
        cur = self._tree[i]
        self._counts[i] += 1
        if value < cur:
            i = 2 * i + 1
        elif value > cur:
            i = 2 * i + 2
        else:
            return
    raise ValueError("Value %s not contained in tree." "Also, the counts are now messed up." % value)