Update fmt docstring

pygmt/figure.py

@@ -154,16 +154,17 @@ def psconvert(self, **kwargs):
  Append the size of the subsample box (1, 2, or 4) [4]. Default is
  no anti-aliasing (same as bits = 1).
  fmt : str
- Sets the output format, where *b* means BMP, *e* means EPS, *E*
- means EPS with PageSize command, *f* means PDF, *F* means
- multi-page PDF, *j* means JPEG, *g* means PNG, *G* means
- transparent PNG (untouched regions are transparent), *m* means PPM,
- *s* means SVG, and *t* means TIFF [default is JPEG]. To ``'bjgt'``
- you can append ``'+m'`` in order to get a monochrome (grayscale)
- image. The EPS format can be combined with any of the other
- formats. For example, ``'ef'`` creates both an EPS and a PDF file.
- Using ``'F'`` creates a multi-page PDF file from the list of input
- PS or PDF files. It requires the *prefix* option.
+ Sets the output format, where **b** means BMP, **e** means EPS,
+ **E** means EPS with PageSize command, **f** means PDF, **F** means
+ multi-page PDF, **j** means JPEG, **g** means PNG, **G** means
+ transparent PNG (untouched regions are transparent), **m** means
+ PPM, **s** means SVG, and **t** means TIFF [default is JPEG]. To
+ **b**\|\ **j**\|\ **g**\|\ **t**\ , optionally append **+m** in
+ order to get a monochrome (grayscale) image. The EPS format can be
+ combined with any of the other formats. For example, **ef** creates
+ both an EPS and a PDF file. Using **F** creates a multi-page PDF
+ file from the list of input PS or PDF files. It requires the
+ ``prefix`` option.
  """
  kwargs = self._preprocess(**kwargs)
  # Default cropping the figure to True