Implement loaidng a Session from file

Issue #57

Author: ebrahimebrahim

src/openlifu/db/database.py

@@ -9,7 +9,7 @@
 import glob
 from typing import Literal, Optional
 from openlifu.plan import Protocol, Solution
-from openlifu.db import Subject
+from openlifu.db import Subject, Session
 OnConflictOpts = Literal['error', 'overwrite', 'skip']
 
 
@@ -425,7 +425,6 @@ def load_all_protocols(self):
             raise FileNotFoundError("Protocols file not found.")
 
     def load_session(self, subject, session_id, options=None):
-        raise NotImplementedError("Session.from_file is not yet implemented")
         if options is None:
             options = {}
         session_filename = self.get_session_filename(subject.id, session_id)

src/openlifu/db/session.py

@@ -5,6 +5,7 @@
 from openlifu.xdc import Transducer
 from openlifu.util.strings import sanitize
 import xarray
+import json
 
 @dataclass
 class Session:
@@ -49,6 +50,17 @@ def __post_init__(self):
         else:
             self.markers = list(self.markers)
 
+    @staticmethod
+    def from_file(filename):
+        """
+        Create a Session from a file
+
+        :param filename: Name of the file to read
+        :returns: Session object
+        """
+        with open(filename, 'r') as f:
+            return Session.from_dict(json.load(f))
+
     @staticmethod
     def from_dict(d):
         """