add isData

segment.py

@@ -49,7 +49,6 @@ class Segment():
         for i in range(bound):
             self.bytes.append(data[i])
             
-
     def get_data(self):
         data=[]
         ptr = self.DATA_PTR   # pointer to data in segment
@@ -79,6 +78,9 @@ class Segment():
     def getFIN(self):
         return self.bytes[8] & 0b10000000
 
+    def isData(self):
+        return not self.bytes[8]
+
     def get_checksum(self):
         return  self.bytes[10] << 8 + self.bytes[11]