src/UploaderManager.php
protected function isProviderAliasExists($provider)
    {
        return array_key_exists($provider, $this->providers) || array_key_exists($provider, $this->customProviders);
    }
protected function isProviderAliasExists($provider)
    {
        return array_key_exists($provider, $this->providers) || array_key_exists($provider, $this->customProviders);
    }
Determine if the given provider alias is already exists in the default and custom providers array.

@param  string  $provider
@return bool