I'm getting a LibraryError talking about "non-empty metadata" when processing tree sequences e.g. from Relate

[hyanwong]

When e.g. you try to simplify a tree sequence from Relate, you get:

LibraryError: Can't squash, flush, simplify or link ancestors with edges that have non-empty metadata. (TSK_ERR_CANT_PROCESS_EDGES_WITH_METADATA)

E.g. see #3057. How do you solve this?

[hyanwong]

Some software, such as Relate, adds metadata to the edges of tree sequence. If you don't need this metadata, the easiest thing is to remove it. As of tskit 0.6.0 and higher, the easiest way is to use the drop_metadata method:

ts = tskit.load("relate_ts.trees")
tables = ts.dump_tables()
tables.edges.drop_metadata()
ts = tables.tree_sequence()
# Do whatever you want with the new `ts`
ts.simplify(range(10))