Use algos.is_monotonic instead of Index instant

Author: makbigc

pandas/core/indexes/interval.py

@@ -5,6 +5,7 @@
 import numpy as np
 
 from pandas._libs import Timedelta, Timestamp
+from pandas._libs.algos import is_monotonic
 from pandas._libs.interval import Interval, IntervalMixin, IntervalTree
 from pandas.compat import add_metaclass
 from pandas.util._decorators import Appender, cache_readonly
@@ -451,7 +452,7 @@ def is_monotonic_increasing(self):
         values = [self.right, self.left]
 
         sort_order = np.lexsort(values)
-        return Index(sort_order).is_monotonic
+        return is_monotonic(sort_order, False)[0]
 
     @cache_readonly
     def is_monotonic_decreasing(self):