Create hosted user annotations [1685] (#1726)

* add function to retrieve latest annotation from db, db updates

* read and write tiledb arrays

* adding tests

server/common/annotations/annotations.py

@@ -0,0 +1,78 @@
+from abc import ABCMeta, abstractmethod
+
+import fastobo
+import fsspec
+from server.common.errors import OntologyLoadFailure
+
+from server.common.utils import series_to_schema
+
+
+class Annotations(metaclass=ABCMeta):
+    """ baseclass for annotations, including ontologies"""
+
+    """ our default ontology is the PURL for the Cell Ontology.
+    See http://www.obofoundry.org/ontology/cl.html """
+    DefaultOnotology = "http://purl.obolibrary.org/obo/cl.obo"
+
+    def __init__(self):
+        self.ontology_data = None
+
+    def load_ontology(self, path):
+        """Load and parse ontologies - currently support OBO files only."""
+        if path is None:
+            path = self.DefaultOnotology
+
+        try:
+            with fsspec.open(path) as f:
+                obo = fastobo.iter(f)
+                terms = filter(lambda stanza: type(stanza) is fastobo.term.TermFrame, obo)
+                names = [tag.name for term in terms for tag in term if type(tag) is fastobo.term.NameClause]
+                self.ontology_data = names
+
+        except FileNotFoundError as e:
+            raise OntologyLoadFailure("Unable to find OBO ontology path") from e
+
+        except SyntaxError as e:
+            raise OntologyLoadFailure("Syntax error loading OBO ontology") from e
+
+        except Exception as e:
+            raise OntologyLoadFailure("Error loading OBO file") from e
+
+    def get_schema(self, data_adaptor):
+        schema = []
+        labels = self.read_labels(data_adaptor)
+        if labels is not None and not labels.empty:
+            for col in labels.columns:
+                col_schema = dict(name=col, writable=True)
+                col_schema.update(series_to_schema(labels[col]))
+                schema.append(col_schema)
+
+        return schema
+
+    @abstractmethod
+    def set_collection(self, name):
+        """set or create a new annotation collection"""
+        pass
+
+    @abstractmethod
+    def read_labels(self, data_adaptor):
+        """Return the labels as a pandas.DataFrame"""
+        pass
+
+    @abstractmethod
+    def write_labels(self, df, data_adaptor):
+        """Write the labels (df) to a persistent storage such that it can later be read"""
+        pass
+
+    def update_parameters(self, parameters, data_adaptor):
+        """Update configuration parameters that describe information about the annotations feature"""
+        params = {}
+        params["annotations"] = True
+
+        if self.ontology_data:
+            params["annotations_cell_ontology_enabled"] = True
+            params["annotations_cell_ontology_terms"] = self.ontology_data
+        else:
+            params["annotations_cell_ontology_enabled"] = False
+
+        parameters.update(params)