• Refactoring the aggregate code
  • Split the big aggregate pipeline function in a function for each stage
  • Move all the code for the aggregate pipeline to the aggregate module
• Consider w=1 as the default value in WriteConcern
• Increase test coverage in aggregate.py and fix some date operators
• Remove dead code and test all lines in the helpers module
• Increase test coverage in filtering.py
• Lint for keyword-arg-before-vararg and redefined-outer-name
• Implement basic system variables in aggregation expressions
• Mark Variables in Aggregation Expressions as not implemented
• Add the codecov badge
• Skip flaky test when running PyPy
• Improve test coverage by adding few more tests and dropping useless code
• Remove unused private function
• Upload coverage to codecov.io
• Fix $push update operations in corner cases
• Implement the $slice operator for $push update operations
• Fix usage of $ne and $nin used on repeated fields and/or with other operators
• Fix insert_many using generators
• Fix a flaky test in PyPy