feat(compatibility): Python3.6 compatibility

.travis.yml

@@ -5,6 +5,7 @@ python:
   - 3.9
   - 3.8
   - 3.7
+  - 3.6
 cache:
   directories:
   - "$HOME/.cache/pip"

setup.py

@@ -59,7 +59,7 @@ setup(
     url=PROJECT_URL,
     download_url=DOWNLOAD_URL,
     license="MIT",
-    python_requires=">=3.7",
+    python_requires=">=3.6",
     install_requires=INSTALL_REQUIRES,
     extras_require={
         "datasets": DATASETS,
@@ -78,6 +78,9 @@ setup(
         "License :: OSI Approved :: MIT License",
         "Natural Language :: English",
         "Programming Language :: Python :: 3.9",
+        "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.7",
+        "Programming Language :: Python :: 3.6",
         "Operating System :: OS Independent",
         "Topic :: Scientific/Engineering :: Artificial Intelligence",
         "Topic :: Software Development :: Libraries",