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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def hash_stream(fileobj, hasher=None, blocksize=65536):
 """Read from fileobj stream, return hash of its contents. Args: fileobj: File-like object with read() hasher: Hash object such as hashlib.sha1(). Defaults to sha1. blocksize: Read from fileobj this many bytes at a time. """

    hasher = hasher or hashlib.sha1()
    buf = fileobj.read(blocksize)
    while buf:
        hasher.update(buf)
        buf = fileobj.read(blocksize)
    return hasher