We claim, the ornamental design for a cyclist helmet, as shown and described.
FIG. 1 is a front and side perspective view of the cyclist helmet showing our new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a side elevation view thereof taken from the left of FIG. 2;
FIG. 4 is a side elevation view thereof taken from the right of FIG. 2;
FIG. 5 is a top plan view thereof; and,
FIG. 6 is a rear elevation view thereof.
Said drawings include certain features which are shown in broken lines having a dash-dot-dash pattern for illustrative purposes only in order to show environment, and form no part of the claimed design. The broken lines which define the bounds of the claimed design are shown in a dashed pattern, and form no part thereof.