How do I implement some of the following line substitutions?

as the following example:
I want to replace packet in the line that contains bytes with bytes .

    **rx_bytes2_blob = BlobField("rx proto2 packets" , item_type = int)**--->rx_bytes2_blob = BlobField("rx proto2 *bytes*" , item_type = int)

I checked that there is on the Internet: G code by yy but this is not in line with my habit. I usually replace it from xx line to yy line.
tried, xx,yy/bytes/s/packets/bytes/g; probably converted all packets into bytes .

    rx_proto2_blob = BlobField("rx proto2, bytes is the 2nd, ...", item_type = int)
    rx_packets2_blob = BlobField("rx proto2 packets" , item_type = int)
    rx_bytes2_blob = BlobField("rx proto2 packets" , item_type = int)

    rx_proto3_blob = BlobField("rx proto3, bytes is the 3rd, ...", item_type = int)
    rx_packets3_blob = BlobField("rx proto3 packets" , item_type = int)
    rx_bytes3_blob = BlobField("rx proto3 packets" , item_type = int)

    rx_proto4_blob = BlobField("rx proto4, bytes is the largest, ...", item_type = int)
    rx_packets4_blob = BlobField("rx proto4 packets" , item_type = int)
    rx_bytes4_blob = BlobField("rx proto4 packets" , item_type = int)

    rx_proto5_blob = BlobField("rx proto5, bytes is the largest, ...", item_type = int)
    rx_packets5_blob = BlobField("rx proto5 packets" , item_type = int)
    rx_bytes5_blob = BlobField("rx proto5 packets" , item_type = int)

    rx_proto6_blob = BlobField("rx proto6, bytes is the largest, ...", item_type = int)
    rx_packets6_blob = BlobField("rx proto6 packets" , item_type = int)
    rx_bytes6_blob = BlobField("rx proto6 packets" , item_type = int)
Mar.06,2021
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