Add parameter and return types to importDXF (#1205)

* add parameter and return types
* fix param filename case in docstring
* fix disjointed paragraph in rendered docs
* format example code with black

cadquery/occ_impl/importers/__init__.py

@@ -1,4 +1,5 @@
 from math import pi
+from typing import List
 
 from ... import cq
 from ..shapes import Shape
@@ -67,14 +68,16 @@ def importStep(fileName):
     return cq.Workplane("XY").newObject(solids)
 
 
-def importDXF(filename, tol=1e-6, exclude=[], include=[]):
+def importDXF(
+    filename: str, tol: float = 1e-6, exclude: List[str] = [], include: List[str] = []
+) -> "cq.Workplane":
     """
     Loads a DXF file into a Workplane.
 
     All layers are imported by default.  Provide a layer include or exclude list
-     to select layers.  Layer names are handled as case-insensitive.
+    to select layers.  Layer names are handled as case-insensitive.
 
-    :param fileName: The path and name of the DXF file to be imported
+    :param filename: The path and name of the DXF file to be imported
     :param tol: The tolerance used for merging edges into wires
     :param exclude: a list of layer names not to import
     :param include: a list of layer names to import

doc/importexport.rst

@@ -57,10 +57,8 @@ Importing a DXF profile with default settings and using it within a CadQuery scr
     import cadquery as cq
 
     result = (
-        cq.importers.importDXF('/path/to/dxf/circle.dxf')
-        .wires().toPending()
-        .extrude(10)
-        )
+        cq.importers.importDXF("/path/to/dxf/circle.dxf").wires().toPending().extrude(10)
+    )
 
 Note the use of the :py:meth:`Workplane.wires` and :py:meth:`Workplane.toPending` methods to make the DXF profile 
 ready for use during subsequent operations. Calling ``toPending()`` tells CadQuery to make the edges/wires available