def core(corename)
      raise "Core #{corename} not found" unless cores.include? corename.to_s
      SimpleSolrClient::Core.new(@base_url, corename.to_s)
    end
def core(corename)
      raise "Core #{corename} not found" unless cores.include? corename.to_s
      SimpleSolrClient::Core.new(@base_url, corename.to_s)
    end
Get a client specific to the given core2
 @param [String] corename The name of the core (which must already exist!)
 @return [SimpleSolrClient::Core]