IMP: collate contig-maps (#405)

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# Description
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This PR adds function to collate contig-maps. Related to
[#14](bokulich-lab/q2-mag#14)






# AI Disclosure
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- [] NO AI USED.
- [x] AI USED.


# AI Usage Details
Claude (Sonnet 5) was used to generate descriptors in plugin_setup.py.

Author: ZuzanaSebb

q2_types/feature_map/__init__.py

@@ -14,9 +14,10 @@
 from ._types import (
     FeatureMap, MAGtoContigs, TaxonomyToContigs, FunctionToContigs
 )
+from ._methods import collate_contig_maps
 
 __all__ = [
     "FeatureMap", "MAGtoContigs", "MAGtoContigsFormat", "MAGtoContigsDirFmt",
     "TaxonomyToContigs", "FeatureMapFormat",
-    "FeatureMapDirFmt", "FunctionToContigs"
+    "FeatureMapDirFmt", "FunctionToContigs", "collate_contig_maps"
 ]

q2_types/feature_map/_methods.py

@@ -0,0 +1,15 @@
+# ----------------------------------------------------------------------------
+# Copyright (c) 2026, QIIME 2 development team.
+#
+# Distributed under the terms of the Modified BSD License.
+#
+# The full license is in the file LICENSE, distributed with this software.
+# ----------------------------------------------------------------------------
+
+
+def collate_contig_maps(contig_maps: dict) -> dict:
+    collated_contig_maps = {}
+    for contig_map in contig_maps:
+        collated_contig_maps.update(contig_map)
+
+    return collated_contig_maps

q2_types/feature_map/tests/test_methods.py

@@ -0,0 +1,29 @@
+# ----------------------------------------------------------------------------
+# Copyright (c) 2026, QIIME 2 development team.
+#
+# Distributed under the terms of the Modified BSD License.
+#
+# The full license is in the file LICENSE, distributed with this software.
+# ----------------------------------------------------------------------------
+from qiime2.plugin.testing import TestPluginBase
+
+from q2_types.feature_map import collate_contig_maps
+
+
+class TestCollateContigMaps(TestPluginBase):
+    package = "q2_types.feature_map.tests"
+
+    def test_collate_contig_maps(self):
+        contig_maps = [
+            {"mag1": ["contig1", "contig2"]},
+            {"mag2": ["contig3"], "mag3": ["contig4", "contig5"]},
+        ]
+
+        obs = collate_contig_maps(contig_maps)
+
+        exp = {
+            "mag1": ["contig1", "contig2"],
+            "mag2": ["contig3"],
+            "mag3": ["contig4", "contig5"],
+        }
+        self.assertDictEqual(exp, obs)

q2_types/plugin_setup.py

@@ -25,6 +25,7 @@
     PairedEndSequencesWithQuality, Contigs
 )
 from q2_types.feature_data import FeatureData, Sequence
+from q2_types.feature_map import FeatureMap, MAGtoContigs, collate_contig_maps
 from q2_types.genome_data import (
     Orthologs, GenomeData, NOG, Loci, DNASequence, Genes, Proteins
 )
@@ -249,6 +250,19 @@
                 "and collates them into a single artifact.",
 )
 
+plugin.methods.register_function(
+    function=collate_contig_maps,
+    inputs={"contig_maps": List[FeatureMap[MAGtoContigs]]},
+    parameters={},
+    outputs={"collated_contig_maps": FeatureMap[MAGtoContigs]},
+    input_descriptions={
+        "contig_maps": "A collection of MAG-to-contig maps to be collated."
+    },
+    name="Collate MAG-to-contig maps",
+    description="Takes a collection of FeatureMap[MAGtoContigs]s "
+                "and collates them into a single artifact.",
+)
+
 KRAKEN2_REPORTS = TypeMatch([
     SampleData[Kraken2Reports % Properties('reads')],
     SampleData[Kraken2Reports % Properties('contigs')],