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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _load_shader(filename):
 """Load a shader file."""

    curdir = op.dirname(op.realpath(__file__))
    glsl_path = op.join(curdir, 'glsl')
    path = op.join(glsl_path, filename)
    with open(path, 'r') as f:
        return f.read()