loading from stackoverflow.csv
number of nulls in each col:
Unnamed: 0         0
Age                0
Accessibility      0
EdLevel            0
Employment         0
Gender             0
MentalHealth       0
MainBranch         0
YearsCode          0
YearsCodePro       0
Country            0
PreviousSalary     0
HaveWorkedWith    63
ComputerSkills     0
Employed           0
dtype: int64

number of records: 73462
removing unused columns: 'Accessibility', 'HaveWorkedWith', 'Employment'
removing rows of non-devs
removing outliers of >42 years pro experience
cleaned data set number of records: 67265