'Sets the length of the sequence to the specified number of steps.
If the event sequence is not long enough, will pad  to make the sequence
the specified length. If it is too long, it will be truncated to the
requested length.
Args:
steps: How many steps long the event sequence should be.
from_left: Whether to add/remove from the left instead of right.'

@abc.abstractmethod
def set_length(self, steps, from_left=False):

    pass
