Add lakes alias to Figure.coast() (#781)

* Add lakes alias to coast in base_plotting.py

* Changing color to fill

* Update coast docstring to r-string and change line lengths

* Add test for lake alias to test_coast.py

* Run make format

* Update pygmt/base_plotting.py

Co-authored-by: Dongdong Tian <seisman.info@gmail.com>

* Update pygmt/base_plotting.py

Co-authored-by: Dongdong Tian <seisman.info@gmail.com>

* Fixing doc string length

Co-authored-by: Dongdong Tian <seisman.info@gmail.com>

pygmt/base_plotting.py

@@ -60,6 +60,7 @@ def _preprocess(self, **kwargs):  # pylint: disable=no-self-use
         R="region",
         J="projection",
         A="area_thresh",
+        C="lakes",
         B="frame",
         D="resolution",
         I="rivers",
@@ -77,7 +78,7 @@ def _preprocess(self, **kwargs):  # pylint: disable=no-self-use
     )
     @kwargs_to_strings(R="sequence", p="sequence")
     def coast(self, **kwargs):
-        """
+        r"""
         Plot continents, shorelines, rivers, and borders on maps
 
         Plots grayshaded, colored, or textured land-masses [or water-masses] on
@@ -110,8 +111,13 @@ def coast(self, **kwargs):
             hierarchical level that is lower than min_level or higher than
             max_level will not be plotted.
         {B}
-        C : str
-            Set the shade, color, or pattern for lakes and river-lakes.
+        lakes : str or list
+            *fill*\ [**+l**\ |**+r**\ ]
+            Set the shade, color, or pattern for lakes and river-lakes. The
+            default is the fill chosen for wet areas set by the ``water``
+            argument. Optionally, specify separate fills by appending
+            **+l** for lakes or **+r** for river-lakes, and passing multiple
+            strings in a list.
         resolution : str
             Selects the resolution of the data set to use ((f)ull, (h)igh,
             (i)ntermediate, (l)ow, and (c)rude).

pygmt/tests/test_coast.py

@@ -57,6 +57,7 @@ def test_coast_aliases():
         Y="a10c",
         p="135/25",
         t=13,
+        C="blue",
     )
     fig_test.coast(
         region=[-30, 30, -40, 40],  # R
@@ -74,6 +75,7 @@ def test_coast_aliases():
         yshift="a10c",  # Y
         perspective=[135, 25],  # p
         transparency=13,  # t
+        lakes="blue",  # C
     )
     return fig_ref, fig_test