adding constant strings to avoid typo errors

src/alogamous/log_line_parser.py

@@ -1,6 +1,12 @@
 from __future__ import annotations
 
 
+class LineType:
+    HEADER_LINE = "header line"
+    LOG_LINE = "log line"
+    UNSTRUCTURED_LINE = "unstructured line"
+
+
 class LogLineParser:
     def __init__(self, header_line: str, expected_fields: list[str], seperator: str):
         self.header_line = header_line
@@ -10,11 +16,11 @@ def __init__(self, header_line: str, expected_fields: list[str], seperator: str)
 
     def parse(self, line):
         if line == self.header_line:
-            return {"type": "header line", "line": line}
+            return {"type": LineType.HEADER_LINE, "line": line}
         if line.count(self.separator) == self.separator_count:
-            parsed_line = {"type": "log line"}
+            parsed_line = {"type": LineType.LOG_LINE}
             separated_line = line.split(self.separator)
             for index in range(len(self.expected_fields)):
                 parsed_line[self.expected_fields[index]] = separated_line[index]
             return parsed_line
-        return {"type": "unstructured line", "line": line}
+        return {"type": LineType.UNSTRUCTURED_LINE, "line": line}