system/Router/RouteCollection.php
public function getFilterForRoute(string $search): string
	{
		if (! $this->isFiltered($search))
		{
			return '';
		}

		return $this->routesOptions[$search]['filter'];
	}
public function getFilterForRoute(string $search): string
	{
		if (! $this->isFiltered($search))
		{
			return '';
		}

		return $this->routesOptions[$search]['filter'];
	}
Returns the filter that should be applied for a single route, along
with any parameters it might have. Parameters are found by splitting
the parameter name on a colon to separate the filter name from the parameter list,
and the splitting the result on commas. So:

'role:admin,manager'

has a filter of "role", with parameters of ['admin', 'manager'].

@param string $search

@return string