Requirements: drop NumPy to 1.19.5 so it works with Python 3.6; add extras

We still recommend `numpy>=1.21` for typing support.

Use DSS C-API 0.12.0b9

Author: PMeira

.github/workflows/builds.yml

@@ -3,7 +3,7 @@ name: Builds
 # TODO: generalize steps
 
 env:
-  DSS_CAPI_TAG: 0.12.0b8
+  DSS_CAPI_TAG: 0.12.0b9
   ARTIFACTS_FOLDER: '${{ github.workspace }}/artifacts'
 
 on: 

dss/IObj.py

@@ -7,14 +7,21 @@
 '''
 from typing import Union, List, AnyStr
 import numpy as np
-import numpy.typing as npt
 from .enums import DSSJSONFlags
 
 try:
     from enum import IntEnum
 except:
     from aenum import IntEnum
 
+try:
+    import numpy.typing as npt
+    npt.NDArray[np.float64]
+except:
+    class npt:
+        NDArray = List
+
+
 from ._cffi_api_util import Base
 
 class BatchFloat64ArrayProxy:

setup.py

@@ -104,7 +104,8 @@
             #'dss_build.py:ffi_builder_CapUserControl'
         ],
     ext_package="dss",
-    install_requires=["cffi>=1.11.2", "numpy>=1.21"],
+    install_requires=["cffi>=1.11.2", "numpy>=1.19.5"],
+    extras_require={'plot': ["matplotlib", "scipy"]}, #TODO: test which versions should work
     tests_require=["zstandard", "scipy"],
     zip_safe=False,
     classifiers=[