def update_gcm_channel(ApplicationId=None, GCMChannelRequest=None):
    """
    Use to update the GCM channel for an app.
    
    
    :example: response = client.update_gcm_channel(
        ApplicationId='string',
        GCMChannelRequest={
            'ApiKey': 'string'
        }
    )
    
    
    :type ApplicationId: string
    :param ApplicationId: [REQUIRED]

    :type GCMChannelRequest: dict
    :param GCMChannelRequest: [REQUIRED] Google Cloud Messaging credentials
            ApiKey (string) -- Platform credential API key from Google.
            

    :rtype: dict
    :return: {
        'GCMChannelResponse': {
            'ApplicationId': 'string',
            'CreationDate': 'string',
            'Credential': 'string',
            'Id': 'string',
            'IsArchived': True|False,
            'LastModifiedBy': 'string',
            'LastModifiedDate': 'string',
            'Platform': 'string',
            'Version': 123
        }
    }
    
    
    :returns: 
    (dict) -- 200 response
    GCMChannelResponse (dict) -- Google Cloud Messaging channel definition
    ApplicationId (string) -- The ID of the application to which the channel applies.
    CreationDate (string) -- When was this segment created
    Credential (string) -- The GCM API key from Google.
    Id (string) -- The unique channel ID.
    IsArchived (boolean) -- Is this channel archived
    LastModifiedBy (string) -- Who last updated this entry
    LastModifiedDate (string) -- Last date this was updated
    Platform (string) -- The platform type. Will be GCM
    Version (integer) -- Version of channel
    
    
    
    
    
    """
    pass
