- fixed matplot lib import
- fixed samples query (v definition_
- fixed frequency and labels logic

if added to samples query to check if c in self

conditions input for the test plot should be a list for strings rather than a string

previously samples used to check if c in self and that would pass the unit test 
The output would be a graph with no plots but a legend with non existent conditions
The correct output should have no conditions in the legend for non existent keys
Hence in the case of conditions being supplied through kwargs it need to be checked with self(conditions exist in self or not)