Add user-generated annotations tests to the server (#1164)

* Add user-generated annotations tests to the server

Partially completes https://github.com/chanzuckerberg/cellxgene/issues/969

* Auto-format python code

* @skip_if: passing lambdas > than property strings

* Respond to feedback from @bkmartinjr

server/data_common/matrix_loader.py

@@ -135,7 +135,6 @@ class MatrixDataType(Enum):
 
 
 class MatrixDataLoader(object):
-
     def __init__(self, location, etype=None):
         self.location = location
         if etype is None:
@@ -145,9 +144,11 @@ class MatrixDataLoader(object):
         self.matrix_type = None
         if self.etype == MatrixDataType.H5AD:
             from server.data_anndata.anndata_adaptor import AnndataAdaptor
+
             self.matrix_type = AnndataAdaptor
         elif self.etype == MatrixDataType.CXG:
             from server.data_cxg.cxg_adaptor import CxgAdaptor
+
             self.matrix_type = CxgAdaptor
 
     def matrix_data_type(self):