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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 encode_bytes(src_buf, dst_file):
 """Encode a buffer length followed by the bytes of the buffer itself. Parameters src_buf: bytes Source bytes to be encoded. Function asserts that 0 <= len(src_buf) <= 2**16-1. dst_file: file File-like object with write method. Returns ------- int Number of bytes written to `dst_file`. """

    if not isinstance(src_buf, bytes):
        raise TypeError('src_buf must by bytes.')

    len_src_buf = len(src_buf)
    assert 0 <= len_src_buf <= 2**16-1
    num_written_bytes = len_src_buf + 2

    len_buf = FIELD_U16.pack(len_src_buf)
    dst_file.write(len_buf)
    dst_file.write(src_buf)

    return num_written_bytes