RP serialconsole: enableConsole/disableConsole REST call failed

Hello, I'm doing the CLI codegen validation for RP serialconsole.
I found the simple enableConsole/disableConsole calling always get error 415 from service side. Below is my HTTP request/response details:

Request URL: 'https://management.azure.com/subscriptions/92f95d8f-3c67-4124-91c7-8cf07cdbf241/providers/Microsoft.SerialConsole/consoleServices/default/enableConsole?api-version=REDACTED'
Request method: 'POST'
Request headers:
'Accept': 'application/json'
'x-ms-client-request-id': 'a6516242-8ab6-11ea-b42f-70bc107fb75f'
'CommandName': 'REDACTED'
'ParameterSetName': 'REDACTED'
'User-Agent': 'AZURECLI/2.4.0 (PIP) azsdk-python-mgmt-serialconsole/0.1.0 Python/3.8.1 (Windows-10-10.0.18362-SP0)'
'Authorization': 'REDACTED'

--------------------------------------------------

Response status: 415
Response headers:
'Cache-Control': 'no-cache'
'Pragma': 'no-cache'
'Content-Length': '27'
'Content-Type': 'text/plain; charset=utf-8'
'Expires': '-1'
'x-ms-ratelimit-remaining-subscription-writes': '1199'
'x-ms-request-id': 'c96e3f8e-fd4b-48e0-b4bf-6a0ea652f5c8'
'x-ms-correlation-request-id': 'c96e3f8e-fd4b-48e0-b4bf-6a0ea652f5c8'
'x-ms-routing-request-id': 'JAPANEAST:20200430T074612Z:c96e3f8e-fd4b-48e0-b4bf-6a0ea652f5c8'
'Strict-Transport-Security': 'max-age=31536000; includeSubDomains'
'X-Content-Type-Options': 'nosniff'
'Date': 'Thu, 30 Apr 2020 07:46:11 GMT'
Response content:
415: Unsupported Media Type

Start by inspecting the RP serialconsole REST specification and the generated CLI request for the enableConsole and disableConsole operations. Reproduce the shown POST request and compare its headers and body with the service contract; done means both operations no longer receive HTTP 415 responses.

Written by the indexing model from the issue text.