fix: move cifti to check to top level function

- create property is_cifti
- rename conversion function as_cifti

Author: satra

nibabel/loadsave.py

@@ -39,7 +39,12 @@ def load(filename):
     img : ``SpatialImage``
        Image of guessed type
     '''
-    return guessed_image_type(filename).from_filename(filename)
+
+    img = guessed_image_type(filename).from_filename(filename)
+    if isinstance(img, Nifti2Image):
+        if img.is_cifti:
+            return img.as_cifti()
+    return img
 
 
 def guessed_image_type(filename):

nibabel/nifti2.py

@@ -232,18 +232,17 @@ class Nifti2Pair(Nifti1Pair):
 class Nifti2Image(Nifti1Image):
     header_class = Nifti2Header
 
-    @classmethod
-    def from_file_map(klass, file_map):
-        img = super(Nifti2Image, klass).from_file_map(file_map)
-        hdr = img.get_header()
+    @property
+    def is_cifti(self):
+        hdr = self.get_header()
         intent_code = hdr.get_intent('code')[0]
-        img.is_cifti = False
+        cifti_header = False
         if intent_code >= 3000 and intent_code < 3100:
-            img.is_cifti = True
-            img = img.to_cifti()
-        return img
+            cifti_header = True
+        return cifti_header
 
-    def to_cifti(self):
+    def as_cifti(self):
+        """Convert NIFTI-2 file to CIFTI"""
         if not self.is_cifti:
             TypeError('Nifti2 image is not a CIFTI file')
         hdr = self.get_header()