Use pd.NA

Author: Daniel Saxton

pandas/_libs/hashtable_class_helper.pxi.in

@@ -11,6 +11,8 @@ WARNING: DO NOT edit .pxi FILE directly, .pxi is generated from .pxi.in
 
 from pandas._libs.tslibs.util cimport get_c_string
 
+import pandas as pd
+
 {{py:
 
 # name, dtype, c_type
@@ -1032,7 +1034,7 @@ cdef class PyObjectHashTable(HashTable):
             val = values[i]
             hash(val)
 
-            if ignore_na and (((val == val) is (val != val))
+            if ignore_na and ((val is pd.NA)
                               or (val != val or val is None)
                               or (use_na_value and val == na_value)):
                 # if missing values do not count as unique values (i.e. if