Set random state in fit rather than __init__
Add specific exception description for ValueError
Change indentation of multiline if-statement
Remove unused variable
Use term callable instead of function in doc string
Add more precise description of is_*_valid parameters
Combine nested if-statements
Remove default perceptron base estimator for integer data type
Add support for sparse feature vectors
Fix indentation of multi-line if-statement
Remove trailing empty line after doc strings
Add test case for sparse feature matrix