Loads a Barrister IDL JSON from the given file and returns a Contract class

    :Parameters:
      fname
        Filename containing Barrister IDL JSON to load

def contract_from_file(fname):
    """
    Loads a Barrister IDL JSON from the given file and returns a Contract class

    :Parameters:
      fname
        Filename containing Barrister IDL JSON to load
    """
    f = open(fname)
    j = f.read()
    f.close()
    return Contract(json.loads(j))