expand style functionality (#75)

* expand style functionality

* add feedback

* Apply suggestions from code review

Co-authored-by: Oriol Abril-Pla <oriol.abril.pla@gmail.com>

---------

Co-authored-by: Oriol Abril-Pla <oriol.abril.pla@gmail.com>

src/arviz_plots/style.py

@@ -1,5 +1,7 @@
 """Style/templating helpers."""
 
+from arviz_base import rcParams
+
 
 def use(name):
     """Set an arviz style as the default style/template for all available backends.
@@ -13,16 +15,77 @@ def use(name):
     -----
     There are some backends where default styles/templates are not supported.
     """
+    ok = False
+
+    try:
+        import matplotlib.pyplot as plt
+
+        if name in plt.style.available:
+            plt.style.use(name)
+            ok = True
+    except ImportError:
+        pass
+
+    try:
+        import plotly.io as pio
+
+        if name in pio.templates:
+            pio.templates.default = name
+            ok = True
+    except ImportError:
+        pass
+
+    if not ok:
+        raise ValueError(f"Style {name} not found.")
+
+
+def available():
+    """List available styles."""
+    styles = {}
+
     try:
         import matplotlib.pyplot as plt
 
-        plt.style.use(name)
+        styles["matplotlib"] = plt.style.available
     except ImportError:
         pass
 
     try:
         import plotly.io as pio
 
-        pio.templates.default = name
+        styles["plotly"] = list(pio.templates)
     except ImportError:
         pass
+
+    return styles
+
+
+def get(name, backend=None):
+    """Get the style/template with the given name.
+
+    Parameters
+    ----------
+    name : str
+        Name of the style/template to get.
+    backend : str
+        Name of the backend to use. Options are 'matplotlib' and 'plotly'.
+        Defaults to ``rcParams["plot.backend"]``.
+    """
+    if backend is None:
+        backend = rcParams["plot.backend"]
+    if backend not in ["matplotlib", "plotly"]:
+        raise ValueError(f"Default styles/templates are not supported for Backend {backend}")
+
+    if backend == "matplotlib":
+        import matplotlib.pyplot as plt
+
+        if name in plt.style.available:
+            return plt.style.library[name]
+
+    elif backend == "plotly":
+        import plotly.io as pio
+
+        if name in pio.templates:
+            return pio.templates[name]
+
+    raise ValueError(f"Style {name} not found.")