If a type is defined for the InputObject variable, the command will only work if the input pipeline contains that object type. An error will be thrown when a different object type is passed. The following example modifies the command to accept pipeline input from Get-Process; it expects objects of the System.Diagnostics.Process type only:

function Get-InputObject {
    [CmdletBinding()]
    param (
        [Parameter(Mandatory, ValueFromPipeline)]
        [System.Diagnostics.Process]$InputObject
    )

    process {
        'Process name {0}' -f $InputObject.Name
    }
}