refine setup.py

setup.py

@@ -4,23 +4,15 @@
 
 from setuptools import setup, Extension
 from Cython.Build import cythonize
-
-class GetNumpyInclude(object):
-    """A lazy include path for numpy.
-    This way numpy isn't imported until it's actually installed,
-    so the `install_requires` argument can handle it properly.
-    """
-    def __str__(self):
-        import numpy
-        return numpy.get_include()
+import numpy as np
 
 
 if __name__ == "__main__":
     extensions = [
         Extension(
             "anomaly_detector.univariate._anomaly_kernel_cython",
             ["src/anomaly_detector/univariate/_anomaly_kernel_cython.pyx"],
-            include_dirs=[GetNumpyInclude()]
+            include_dirs=[np.get_include()]
         )
     ]