Special Seq-annot object structure to mark insertion of annotations
from source location to target location (with mapping).

Seq-annot ::= {
    desc {
        -- optional name of source Seq-annot object
        name <source Seq-annot name>, -- OPTIONAL
        -- target sequence range, should be simple Seq-interval without strand
        region int {
            from <target from>,
            to <target to>,
            id <target Seq-id>
        },
        -- one or more descriptions of annotations' types in source location
        user {
            type str "Seq-annot.data.align", -- if aligns are there
            data {
            }
        },
        user {
            type str "Seq-annot.data.graph", -- if graphs are there
            data {
            }
        },
        user {
            type str "Seq-annot.data.ftable", -- if features are there
            data {
                {
                    label id <feature type>,
                    data int <feature subtype>
                },
                {
                    label id <feature type>,
                    data ints { <feature subtypes> }
                }
            }
        }
    },
    data locs {
        -- source location of annotations
        -- should be only one Seq-loc object
        <source seq-loc with annotations>
    }
}