bool = gl.IsTexture(texture)
gl.IsTexture() returns #GL_TRUE if texture is currently the name of a texture. If texture is zero, or is
a non-zero value that is not currently the name of a texture, or if an error occurs, gl.IsTexture() returns #GL_FALSE.
A name returned by gl.GenTextures(), but not yet associated with a texture by calling gl.BindTexture(), is not the name of a texture.
Please consult an OpenGL reference manual for more information.
#GL_TRUE or #GL_FALSE#GL_INVALID_OPERATION is generated if gl.IsTexture() is executed between the execution of gl.Begin() and the corresponding execution of gl.End().