Functionality & restrictions /// ///
PUBLIC to retrieve all public channels in the account.
/// AppInstanceAdmin can set privacy = PRIVATE to list
/// the private channels in an account.
/// x-amz-chime-bearer request header is mandatory. Use the ARN of the
/// AppInstanceUser or AppInstanceBot that makes the API call
/// as the value in the header.
/// AppInstance.
/// AppInstanceUser or AppInstanceBot that makes
/// the API call.
/// PUBLIC retrieves all the public channels. PRIVATE
/// retrieves private channels. Only an AppInstanceAdmin can retrieve private
/// channels.
///