import numpy as np
def sin_function(angle):
    '''Returns the sin of angle.
    angle should be given in radians'''
    return np.sin(angle)    
    
    
def int_add_function(var1, var2):
    '''function to add integers and only integers
       if allow_casting is True the variables will
       be cast as integers'''
    
    if not isinstance(var1, int):
        if allow_casting:
            var1 = int(var1)
        else:
            raise TypeError("Only integers are allowed")

    if not isinstance(var2, int):
        if allow_casting:
            var2 = int(var2)
        else:
            raise TypeError("Only integers are allowed")

    return var1 + var2