def load_csv(path: str):
    """
    returns (header: list[str], rows: list[list[T]])
    """
    header = []
    rows = []
    for i, line in enumerate(open(path).read().strip().split('\n')):
        if i == 0:
            header = line.split(',')
        else:
            rows.append(eval(line))
    return header, rows

def labeled_rows(header: list, rows: list):
    """
    return a list of dicts,
    transforming each row into a kv map
    """
    new_rows = []
    for row in rows:
        new_rows.append({ header[i]: elem for i, elem in enumerate(row) })
    return new_rows

def last_row_before_t(rows: list, t: float):
    """
    return the last row for which row[time] < t
    """
    prev_row = None
    for row in rows:
        if row["time"] >= t:
            break
        prev_row = row
    return prev_row


def extract_m(row: dict) -> list:
    """
    return [M(state0), M(state1), ...]
    """
    m = []
    for k, v in row.items():
        if k.startswith('M(state') and k.endswith(')'):
            n = int(k[len('M(state'):-1])
            assert n == len(m)
            m.append(v)
    return m