google-api-core 1.20.0 is incompatible with the pinned version of grpc

It looks like the google-api-core 1.20.0 has an issue with required dependency or the lack thereof. This is causing this issue when using datastore:

Traceback (most recent call last):
{{ File "./query_license.py", line 11, in <module>}}
{{ from google.cloud import datastore}}
{{ File "/root/apache-beam-custom/lib/python3.7/site-packages/google/cloud/datastore/_init_.py", line 62, in <module>}}
{{ from google.cloud.datastore.batch import Batch}}
{{ File "/root/apache-beam-custom/lib/python3.7/site-packages/google/cloud/datastore/batch.py", line 24, in <module>}}
{{ from google.cloud.datastore import helpers}}
{{ File "/root/apache-beam-custom/lib/python3.7/site-packages/google/cloud/datastore/helpers.py", line 29, in <module>}}
{{ from google.cloud.datastore_v1.proto import datastore_pb2}}
{{ File "/root/apache-beam-custom/lib/python3.7/site-packages/google/cloud/datastore_v1/_init_.py", line 18, in <module>}}
{{ from google.cloud.datastore_v1.gapic import datastore_client}}
{{ File "/root/apache-beam-custom/lib/python3.7/site-packages/google/cloud/datastore_v1/gapic/datastore_client.py", line 22, in <module>}}
{{ import google.api_core.gapic_v1.client_info}}
{{ File "/root/apache-beam-custom/lib/python3.7/site-packages/google/api_core/gapic_v1/_init_.py", line 26, in <module>}}
{{ from google.api_core.gapic_v1 import method_async # noqa: F401}}
{{ File "/root/apache-beam-custom/lib/python3.7/site-packages/google/api_core/gapic_v1/method_async.py", line 20, in <module>}}
{{ from google.api_core import general_helpers, grpc_helpers_async}}
{{ File "/root/apache-beam-custom/lib/python3.7/site-packages/google/api_core/grpc_helpers_async.py", line 25, in <module>}}
{{ from grpc.experimental import aio}}
{{ ImportError: cannot import name 'aio' from 'grpc.experimental' (/root/apache-beam-custom/lib/python3.7/site-packages/grpc/experimental/_init_.py)}}