<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def acc_hash(filepath: str, hasher):
 """Accumulate content of file at `filepath` in `hasher`."""

    with open(filepath, 'rb') as f:
        while True:
            chunk = f.read(_BUF_SIZE)
            if not chunk:
                break
            hasher.update(chunk)