Modify unhashable default values in Workload class definition for Python 3.11 (#131)

Signed-off-by: coleramos425 <colramos@amd.com>

src/omniperf_analyze/utils/schema.py

@@ -55,9 +55,9 @@ class ArchConfig:
 
 @dataclass
 class Workload:
-    sys_info: pd.DataFrame = pd.DataFrame()
-    soc_spec: pd.DataFrame = pd.DataFrame()  # TODO: might move it to ArchConfig
-    raw_pmc: pd.DataFrame = pd.DataFrame()
+    sys_info: pd.DataFrame = None
+    soc_spec: pd.DataFrame = None  # TODO: might move it to ArchConfig
+    raw_pmc: pd.DataFrame = None
     dfs: Dict[int, pd.DataFrame] = field(default_factory=dict)
     dfs_type: Dict[int, str] = field(default_factory=dict)
     filter_kernel_ids: List[int] = field(default_factory=list)