[Feature Request] implement `to_labeled_system` and `to_multi_systems` for `QuipGapXYZFormat`

[njzjz]

Summary

Currently, QuipGapXYZFormat only supports from_multi_systems.

dpdata/dpdata/plugins/xyz.py

Lines 50 to 58 in ba31bcd

	@Format.register("quip/gap/xyz")
	@Format.register("quip/gap/xyz_file")
	class QuipGapXYZFormat(Format):
	def from_labeled_system(self, data, **kwargs):
	return data
	def from_multi_systems(self, file_name, **kwargs):
	# here directory is the file_name
	return QuipGapxyzSystems(file_name)

Implement to_labeled_system and to_multi_systems for QuipGapXYZFormat.

Detailed Description

to_multi_systems: may dump all systems in one file.

Further Information, Files, and Links

No response