Demes

- Fixed the use of numpy strings for deme names.
({user}`terhorst`, {user}`grahamgower`, {issue}`495`, {pr}`505`)
- Added `Graph.rename_demes()` method to return a graph with renamed demes.
({user}`aabiddanda`, {pr}`499`)

Better conformance to the spec. Minor discrepancies between
demes-python and the reference implementation have been resolved.

- Dropped support for Python 3.6
({user}`grahamgower`, {issue}`445`, {pr}`446`)
- Reject bad defaults, even if they're not used.
({user}`grahamgower`, {issue}`443`, {pr}`430`)
- Set encoding to UTF-8 explicitly. This fixes unicode deme names on Windows.
({user}`grahamgower`, {pr}`430`)
- `Graph.description` and `Deme.description` can no longer be `None`.
A missing description will now be resolved to the empty string.
({user}`grahamgower`, {issue}`429`, {pr}`430`)
- `Graph.generation_time` can no longer be `None`.
When `time_units` are generations, a missing `generation_time` will now
be resolved to 1 and other values are an error.
({user}`grahamgower`, {issue}`429`, {pr}`430`)
- Permit selfing_rate + cloning_rate >= 1.
Both values must be between zero and one (inclusive), but the selfing_rate
is now defined as conditional on sexual reproduction (which occurs at
rate `1 - cloning_rate`).
({user}`grahamgower`, {issue}`425`, {pr}`423`)

**New features:**

- Support for the `metadata` field at the toplevel of a YAML file.
The is a dictionary that may contain arbitrary nested data.
({user}`grahamgower`, {issue}`275`, {pr}`392`).

**Bug fixes:**

- The string "Infinity" is now accepted when using `load_all()`,
just like for `load()` and `loads()`.
This fixes loading fully-resolved models with the CLI.
({user}`grahamgower`, {issue}`394`, {pr}`395`).

**Breaking changes:**

- The `demes.hypothesis_strategies.graphs()` function for generating
a random `Graph` has been removed. This was buggy and not usable
as originally intended.
({user}`grahamgower`, {issue}`360`, {pr}`397`).

**New features:**

- Add `load_all()`/`dump_all()` to support multi-document YAML.
({user}`grahamgower`, {issue}`239`, {pr}`335`)
- Add CLI.
({user}`grahamgower`, {pr}`339`)
- Add `to_ms()` function.
({user}`grahamgower`, {issue}`74`, {pr}`354`)
- Allow for "Infinity" as start times for demes and migrations in input
YAMLs and dicts.
({user}`apragsdale`, {issue}`358`, {pr}`386`)


**Breaking changes:**

- A pulse event now allows for simultaneous sources and takes arguments
`sources` and `proportions` instead of `source` and `proportion`. The
sources and proportions must be provided as a list, even when there is
only a single source deme.
({user}`apragsdale`, {pr}`353`)
- Disallow null values and blank entries in input YAML models.
({user}`apragsdale`, {issue}`340`, {pr}`387`)

**Bug fixes:**

- Fix various issues in `from_ms()` with `-es`/`-ej` commands.
({user}`grahamgower`, {issue}`350`, {issue}`351`, {pr}`352`)
- Fix some pulse edge cases when pulse events occur at the same time.
({user}`grahamgower`, {issue}`328`, {issue}`357`, {pr}`362`)
- `todict_simplified()` now properly handles symmetric migrations when the
end times of the demes involved differ.
({user}`apragsdale`, {issue}`384`, {pr}`385`)

**New features**:

- Add `Graph.migration_matrices()` to get the migration matrices for a graph.
({user}`grahamgower`, {issue}`309`, {pr}`320`)
- Add `Deme.size_at()` to get the size of a deme at a given time.
({user}`grahamgower`, {issue}`312`, {pr}`314`)
- Support "linear" as an `Epoch.size_function`.
({user}`noscode`, {issue}`296`, {pr}`310`)
- Downstream test code can now use the `demes.hypothesis_strategies.graphs()`
[hypothesis](https://hypothesis.readthedocs.io/) strategy to generate a
random `Graph`. This is preliminary, and as such is not yet documented,
but is used for testing internally with some success. The API may change
in the future in response to requests from downstream application authors.
({user}`grahamgower`, {issue}`217`, {pr}`294`)
- The string representation for a graph, `Graph.__str__()`, is now the
simplified YAML output.
({user}`grahamgower`, {issue}`235`, {pr}`293`)

**Breaking changes**:

- The undocumented msprime and stdpopsim converters have been removed.
({user}`grahamgower`, {issue}`313`, {pr}`316`)
- The JSON spec doesn't allow serialising infinite float values (although the
Python json library does support this by default). So for JSON output we
instead use the string "Infinity".
({user}`grahamgower`,
[demes-spec70](https://github.com/popsim-consortium/demes-spec/issues/70),
{pr}`311`)

Remove the "demes" console_scripts entry point.
This isn't documented/supported and was left in accidentally.