Get, how much steps will needed for a given branch length.

        Returns:
            float: The age the tree must achieve to reach the given branch length.

def get_steps_branch_len(self, length):
        """Get, how much steps will needed for a given branch length.

        Returns:
            float: The age the tree must achieve to reach the given branch length.
        """
        return log(length/self.length, min(self.branches[0][0]))