Graphormer fix (#21699)

* Removed useless check for backend

* fix style check for graphormer

* Reverted change and corrected requires_backend for cython

* code qual

src/transformers/models/graphormer/collating_graphormer.py

@@ -24,9 +24,7 @@ def convert_to_single_emb(x, offset: int = 512):
 
 
 def preprocess_item(item, keep_features=True):
-    requires_backends(preprocess_item, ["Cython"])
-    if not is_cython_available():
-        raise ImportError("Graphormer preprocessing needs Cython (pyximport)")
+    requires_backends(preprocess_item, ["cython"])
 
     if keep_features and "edge_attr" in item.keys():  # edge_attr
         edge_attr = np.asarray(item["edge_attr"], dtype=np.int64)

src/transformers/utils/import_utils.py

@@ -992,6 +992,11 @@ DECORD_IMPORT_ERROR = """
 decord`. Please note that you may need to restart your runtime after installation.
 """
 
+CYTHON_IMPORT_ERROR = """
+{0} requires the Cython library but it was not found in your environment. You can install it with pip: `pip install
+Cython`. Please note that you may need to restart your runtime after installation.
+"""
+
 BACKENDS_MAPPING = OrderedDict(
     [
         ("bs4", (is_bs4_available, BS4_IMPORT_ERROR)),
@@ -1023,6 +1028,7 @@ BACKENDS_MAPPING = OrderedDict(
         ("accelerate", (is_accelerate_available, ACCELERATE_IMPORT_ERROR)),
         ("oneccl_bind_pt", (is_ccl_available, CCL_IMPORT_ERROR)),
         ("decord", (is_decord_available, DECORD_IMPORT_ERROR)),
+        ("cython", (is_cython_available, CYTHON_IMPORT_ERROR)),
     ]
 )