code: protected String getFilePattern( final Bundle bundle )
      {
          if( m_filePatternManifestHeader != null )
          {
              final Object value = bundle.getHeaders().get( m_filePatternManifestHeader );
              if( value instanceof String && ( (String) value ).trim().length() > 0 )
              {
                  return (String) value;
              }
          }
          return m_filePattern;
      }
docs: Returns the file pattern to be searched by first looking for an entry in the manifest of the bundle specified by
  file pattern manifest header. It will return the default file pattern if:
  - file pattern manifest header is null
  - header is not set
  - header is not a string
  - header is empty
  
  @param bundle bundle containing the manifest
  
  @return found file pattern