You're seeing just the function remove, go back to SlackWeb.Pins module for more information.
Link to this function

remove(channel, optional_params \\ %{})

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Un-pins an item from a channel.

Required Params

  • channel - Channel where the item is pinned to.

Optional Params

  • file - File to un-pin.
  • file_comment - File comment to un-pin.
  • timestamp - Timestamp of the message to un-pin.

Errors the API can return:

  • bad_timestamp - Value passed for timestamp was invalid.
  • file_comment_not_found - File comment specified by file_comment does not exist.
  • file_not_found - File specified by file does not exist.
  • message_not_found - Message specified by channel and timestamp does not exist.
  • no_item_specified - One of file, file_comment, or timestamp was not specified.
  • not_pinned - The specified item is not pinned to the channel.
  • permission_denied - The user does not have permission to remove pins from the channel.