m file, keyed by tag key</td></tr>

<tr><td>FILE_EXT</td><td>File extension (JPG, PEF, AVI, etc...) May be undefined if
    file has no extension.</td></tr>

<tr><td>FILE_SEQUENCE</td><td>File sequence number when extracting information</td></tr>

<tr><td>FILE_TYPE</td><td>Root file format type (JPEG, TIFF, RIFF, etc...)</td></tr>

<tr><td>FIRST_EXIF_POS</td><td>Position of first EXIF in file</td></tr>

<tr><td>FMT_EXPR</td><td>The current advanced formatting expression when interpolating tag
    values in 