from typing import Sequence
from typing import List


def flatten(t: Sequence[Sequence]) -> List:
    """
    Flatten a sequence of sequences.

    Parameters
    ----------
    t : Sequence[Sequence]
        The sequence of sequences to flatten.

    Returns
    -------
    List
        Flattened sequence.
    """
    return [item for sublist in t for item in sublist]