Public/Get-TrelloCustomFieldOption.ps1

function Get-TrelloCustomFieldOption {
    [CmdletBinding()]
    param
    (
        [Parameter(Mandatory, ValueFromPipeline)]
        [ValidateNotNullOrEmpty()]
        [pscustomobject]$CustomField
    )
    begin {
        $ErrorActionPreference = 'Stop'
    }
    process {
        try {
            if ('options' -notin $CustomField.PSObject.Properties.Name) {
                throw 'Custom field does not support options.'
            } else {
                $pathParams = "customField/$($CustomField.Id)/options"

                ## Add the custom field ID in the output to support piping to Remove-TrelloCustomFieldId
                $properties = @(
                    '*',
                    @{ 'Name' = 'customFieldId'; Expression = { $CustomField.id } }
                )
                Invoke-PowerTrelloApiCall -PathParameters $pathParams | Select-Object -Property $properties
            }
        } catch {
            $PSCmdlet.ThrowTerminatingError($_)
        }
    }
}