Add inline lists support for Attributes.

Added new tests and updated old tests as this addition is
a regression/backwards incompatibility.

Author: ajoino

tests/test_homogeneous_collections.py

@@ -140,8 +140,31 @@ class RootModel(BaseXmlModel, tag="model"):
     assert_xml_equal(actual_xml, xml)
 
 
+def test_attr_list_extraction():
+    class RootModel(BaseXmlModel, tag="model"):
+        values: List[float] = attr()
+
+    xml = '''
+    <model values="3.14 -1.0 300.0"/>
+    '''
+    # This will fail if scientific notation is used
+    # i.e. if 300 is replaced with 3e2 or 300, the deserializer
+    # will always use the standard notation with the added `.0`.
+    # While this behaviour fails the tests, it shouldn't
+    # matter in practice.
+
+    actual_obj = RootModel.from_xml(xml)
+    expected_obj = RootModel(
+        values = [3.14, -1.0, 3e2]
+    )
+
+    assert actual_obj == expected_obj
+
+    actual_xml = actual_obj.to_xml()
+    assert_xml_equal(actual_xml, xml)
+
+
 def test_homogeneous_definition_errors():
-    breakpoint()
     with pytest.raises(errors.ModelFieldError):
         class TestModel(BaseXmlModel):
             attr1: List[Tuple[int, ...]]
@@ -179,3 +202,4 @@ class TestSubModel(BaseXmlModel):
 
         class TestModel(BaseXmlModel):
             text: List[TestSubModel]
+