code: public void setNamespaceContext(NamespaceContext nsContext) {
          if ( nsContext == null ) {
              String fmsg = XSLMessages.createXPATHMessage( 
                      XPATHErrorResources.ER_ARG_CANNOT_BE_NULL,
                      new Object[] {"NamespaceContext"} );
              throw new NullPointerException( fmsg ); 
          }
          this.namespaceContext = nsContext;
          this.prefixResolver = new JAXPPrefixResolver ( nsContext );
      }
docs: <p>Establishes a namespace context.</p>
  
  @param nsContext Namespace context to use