Resolve "Reduce the amount of uproot.open (to one)"

Closes #36 (closed)

km3io/offline.py

@@ -211,71 +211,6 @@ class OfflineKeys:
         return km3io.definitions.trigger.data
 
 
-class Reader:
-    """Reader for one offline ROOT file"""
-    def __init__(self, file_path):
-        """ Reader class is an offline ROOT file reader. This class is a
-        "very" low level I/O.
-
-        Parameters
-        ----------
-        file_path : str or file-like object
-            The file of interest.
-        """
-        self._tree = uproot.open(file_path)[MAIN_TREE_NAME]
-        self._data = self._tree.lazyarrays(
-            basketcache=uproot.cache.ThreadSafeArrayCache(BASKET_CACHE_SIZE))
-        self._keys = None
-
-    def __getitem__(self, key):
-        """reads data stored in the branch of interest in an Evt tree.
-
-        Parameters
-        ----------
-        key : str
-            name of the branch of interest in event data.
-
-        Returns
-        -------
-        lazyarray
-            Lazyarray of all data stored in the branch of interest. A lazyarray
-            is an array-like object that reads data on demand. Here, only the
-            first and last chunks of data are read in memory, and not all data
-            in the array. The output can be used with all `Numpy's universal
-            functions <https://docs.scipy.org/doc/numpy/reference/ufuncs.html>`
-            .
-
-        Raises
-        ------
-        KeyError
-            Some branches in an offline file structure are "fake branches" and
-            do not contain data. Therefore, the keys corresponding to these
-            fake branches are not read.
-        """
-        keys = self.keys.valid_keys
-        if key not in keys and not isinstance(key, int):
-            raise KeyError(
-                "'{}' is not a valid key or is a fake branch.".format(key))
-        return self._data[key]
-
-    def __len__(self):
-        return len(self._data)
-
-    def __repr__(self):
-        return "<{}: {} entries>".format(self.__class__.__name__, len(self))
-
-    @cached_property
-    def keys(self):
-        """wrapper for all keys in an offline file.
-
-        Returns
-        -------
-        Class
-            OfflineKeys.
-        """
-        return OfflineKeys(self._tree)
-
-
 class OfflineReader:
     """reader for offline ROOT files"""
     def __init__(self, file_path=None):