`self.heap.append` simply appends to the end of the `self.heap` 
Since `self.heap` is just a python list. 
`self.append` calls the append method of the class instance, effectively putting the item in its proper place.

* added relu activation

* added default parameters

A new function, `injection` for dependency injection of globals (for classes and functions that weren't designed for dependency injection).

* add failure_test method to utils

* comment fix

* Update test_learning.py

* Update test_csp.py

* add prob-grammar to notebook

* Update nlp.py

* add weighted choice

* tests for prob grammar + generation

* add test for weighted choice

* Update nlp.py

* Update README.md

* add powerset to utils

* add powerset test

* Create knowledge.py

* Create test_knowledge.py

* add header docstring to knowledge.py

* update learning docstring

* minor edits in knowledge.py

* Fixed truncated_svd

* Moved SVD algorithm to learning.py

* DataFile Update

* Update learning.py

* Update search.py

* Update test_learning.py

* Update test_text.py

* Add files via upload

* Update text.ipynb

* Update search-4e.ipynb

* Create CONTRIBUTING.md

* Delete test_grid.py

* Delete grid.ipynb

* Delete grid.py

* Move grid functions to utils

* Move grid tests to utils

* Update agents.py

* Update mdp.py

* Update search.py

* Create function to initialize random weights

* Add sigmoid derivative function

* Fix flake8 warnings

* Remove unnecessary #noqa

* Fix doctest

* Add Gaussian Function

* Added Tests

Add tests for Continuous Naive Bayes + Means/Standard Deviation

* Update learning.py

* Commenting Fix

* Add test for gaussian

* test for every class

* Update test_learning.py

* Round float results to make sure test passes

* Added test for FIFOQueue

* Updated FIFOQueue

* Updated FIFOQueue

* FIFOQueue using deque

* fixed flake8 warnings

* Adds hashable dict type

* Implemented permutation decoder

* added test for permutation decode

* Optimized permutationdecoder

* relaxed tests

* uses isinstance

* change string format

* Fixed string format

* Adds hashable dict type

* Implemented permutation decoder

* added test for permutation decode

* Optimized permutationdecoder

* relaxed tests

* Exclude test files from flake8 check

* Fix flake8 for main files

* Add flake8 check to build

* Update test_agents.py

pep8 changes, showed flake8 errors

* Update test_agents.py

* Update test_agents.py

* Update test_agents.py

* Update test_text.py

added missing whitespace after comma

* Update utils.py

added space after comma

* Update search.py

added space after comma

* Update probability.py

added space after comma

* Update learning.py

added space after comma

* Update planning.py

added double_tennis_problem

* Update rl.py

In the pseudocode figure 21.8, the first 'if' starts with argument 's', which is the previous state, not s1(i.e, the current state).

* Update search.py

the 'uniform_cost_search' in notebook 'search-4e.ipynb' resembles more to the pseudocode in book.

* Update search.py

* Update search.py

* Update search.py

* Update utils.py

in pseudo code the sequence of arguments is " WEIGHTED-SAMPLE-WITH-REPLACEMENT(N, S, W)"  same must follow in function "particle_filtering" in the file probability.py

* Update learning.py

weight_sample_with_replacement sequence of args

* Update probability.py

 weighted_sample_with_replacement sequence of args

* Update search.py

* Update search.py

Commenting issues fixed (spacing and punctuation was off sometimes).

* Update agents.py

* Update canvas.py

Grammar

* Update grid.py

* Update learning.py

Added period

* Update logic.py

Fix quoting

* Update mdp.py

Fixed quoting

* Update nlp.py

Capitalization and punctuation fixes

* Update planning.py

* Update probability.py

* Update rl.py

'th' to 'the'

* Update search.py

* Update text.py

* Update utils.py

* Update utils.py

* Update utils.py

* Update learning.py

Typo

* Update utils.py

Style: delete excess parentheses. In some of these cases you need to read ahead to see that the paren is not introducing a tuple, for example.

* Replaced mean with standard lib function introduced in 3.4

* #TODO Replaced every with all

* Proper names for variables introduced in 2to3 conversion.

Following a suggestion by C.G.Vedant, changed |implies| to |’==>’|